Solution
Microsoft offers an interface for the Office products, which you can address with the GuiXT Controls.

Please note that Microsoft Project must be installed on the respective PC in this case.

You can address the interface either via JavaScript (callJS command) or via a .NET extension (callVB command). We describe both possibilities below, each of which has advantages and disadvantages.

In this example, we want to export data from SAP Project Builder (CJ20) to Microsoft Project file:

Using a JavaScript call:

Call the following InputScript, which in this example inserts the selected lines into the MS Project file through a callJS call:  

// Variables
 
CreateTable V[inputtab] taskid tasktext taskstart taskend
Set V[absrow] 1 // Absolute row number
Set V[relrow] 1 // Relative row number 
// Change Structure Planning: Basic dates 
Screen SAPLCJTR.0230
  
  GetTableAttribute T[table] firstVisibleRow=FVisRow _
    lastVisibleRow=LVisRow lastRow=LastRow
  
  // First row on screen?
  if V[FVisRow=1]
    goto new_row
  endif
  
  // scroll to first line
  Enter "/scrollToLine=1" table="T[table]"   
  
  label new_screen
  
// Change Structure Planning: Basic dates 
Screen SAPLCJTR.0230
  
  GetTableAttribute T[table] firstVisibleRow=FVisRow _
    lastVisibleRow=LVisRow lastRow=LastRow
  
  Set V[relrow] 1
  
  label new_row
  
  // end of table?
  if V[absrow>&V[LastRow]]
    goto end_of_table
  endif
  
  // end of screen?
  if V[absrow>&V[LVisRow]]
    Enter "/scrollToLine=&V[absrow]" table="T[table]"
    goto new_screen
  endif
  
  Set V[selected] "&cell[table,0,&V[relrow]]"
  
  // Selected?
  
  if V[selected=X]
    
    createstructure V[inputtab_row] taskid tasktext taskstart taskend
    
    Set V[inputtab_row.taskid] "&cell[table,RCWBS-IDENT,&V[relrow]]"
    Set V[inputtab_row.tasktext] "&cell[table,RCWBT-PIDEN,&V[relrow]]"
    Set V[inputtab_row.taskstart] "&cell[table,RCWBT-STERM,&V[relrow]]"
    Set V[inputtab_row.taskend] "&cell[table,RCWBT-ETERM,&V[relrow]]"      
    
    appendrow V[inputtab_row] table="V[inputtab]"
    
  endif
  
  Set V[absrow] &V[absrow] + 1
  Set V[relrow] &V[relrow] + 1
  
  goto new_row 
  
  label end_of_table 
  
  // Export elements to MS Project file  
  callJS addtasks "C:\data\simple_project.mpp" "inputtab"
  
  if V[r] 
    message "E: &V[r]" -statusline
  else
    message "Tasks exported to MS Project" -statusline
  endif
  
  
  // Back to line 1
  Enter "/scrollToLine=1" table="T[Table]" 

The method "addtasks" must be present in the JavaScript library specified in the GuiXT profile and looks like this:

Using a .NET library:

The InputScript from above just slightly changes: The JavaScript call is replaced by a call to the function in the guixt_office.dll file:

// callJS addtasks "C:\data\simple_project.mpp" "inputtab"
callVB  r = guixt_office.msproject.addtasks  _ 
  filename:="C:\data\simple_project.mpp" tasktable:="inputtab"

The corresponding function "addtasks" in VB.NET:

''' 

''' Add a list of tasks to an existing MS Project file
''' 
''' Path to MS project file
''' Name of GuiXT table variable
''' empty string if success, errortext otherwise
Public Function addtasks(filename As String, 
                         tasktable As String) As String

    Dim returnText As String = ""

    Try
        'Create the Application object to interact with MS project
        Dim projectApplication As 
            Microsoft.Office.Interop.MSProject.Application =
        New Microsoft.Office.Interop.MSProject.Application()

        Dim mv As Object = System.Reflection.Missing.Value

        ' Open the MS project file
        projectApplication.FileOpenEx(filename, mv, mv,
                                      mv, mv, mv, mv,
                                      mv, mv, mv, mv,
               Microsoft.Office.Interop.MSProject.PjPoolOpen.pjPoolReadWrite,
                                      mv, mv,
                                      mv, mv, mv)

        ' Get the active project in the file
        Dim project As Microsoft.Office.Interop.MSProject.Project =
            projectApplication.ActiveProject

        ' When createTable is used in GuiXT to fill a table, 
        ' the data is available in JSON format 
        ' We just convert it to an object (array) here
        Dim JSONString = myguixt.GetVariable(tasktable)
        Dim tasks As Object = _ 
             New JavaScriptSerializer().Deserialize(Of Object)(JSONString)

        ' Now we can easily loop through all rows
        For Each t In tasks

            ' Create And add New task
            Dim newTask As Microsoft.Office.Interop.MSProject.Task
            newTask = project.Tasks.Add()

            ' Access the data in column "tasktext" in the current row
            newTask.Name = t("tasktext")

            ' Get the data (string format) and convert to data
            If t("taskstart") <> "" Then
                Dim startDate As New Date
                Date.TryParse(t("taskstart"), startDate)
                newTask.Start = startDate
            End If

            If t("taskend") <> "" Then
                Dim endDate As New Date
                Date.TryParse(t("taskend"), endDate)

                ' We need to add 1 day....
                endDate = endDate.AddDays(1)
                newTask.Finish = endDate

            End If

        Next

        ' Close the file and automatically save
        projectApplication.FileCloseAll(
            Microsoft.Office.Interop.MSProject.PjSaveType.pjSave)

    Catch ex As Exception
        ' Something went wrong: Return the message to GuiXT
        ' so it can be shown on the SAP transaction
        '
        ' e.g. file was not found
        returnText = ex.Message
    End Try

    Return returnText


End Function

Comparison between JavaScript and .NET

Using JavaScript is possible without much effort, but it has the following disadvantage: you have to figure out the methods you need and their parameters, and you have few tools or testing options available. You can therefore also create a .NET library, have tools such as code completion available there and can first test independently of GuiXT and the SAP transaction.

How to create your own .NET dll is described here:
Calling a VB.NET function

You can download the sample project and use it as a basis for your own developments or just use the compiled library.

Download:

Download the .NET project with source-code:
guixt_ms_project.zip

Download the stand-alone classlibrary:
guixt_office.zip

JavaScript library:
guixt_msproject_library.zip

Sample MS Project file:
simple_project.zip

Hint: You might need to "unblock" downloaded .dll files if you want to use them:
Go to file properties (right-click) and choose "unblock".

Components InputAssistant + Controls