Solution 1
(if string is known to be numeric and to consist of no more than 15 digits) 

// Delete leading zeros if not empty        
if V[account]
   set V[account] "&V[account]" + 0
endif

Solution 2
(any string)

// delete leading zeros
label del_zero
  Set V[x] &V[account](1,1)
    if V[x=0]
      Set V[account] "&V[account](2,4000)"
      goto del_zero
  endif
 

Components
InputAssistant