Сложение чисел как строк

s = "000002"
MsgBox Format(s + 1, String(Len(s), "0"))

Dim a As Long
    Static Sub Command1_Click()
    Print Format(a, "00000")
    a = a + 1
End Sub

Sub LongAdd(A As String, B As String, C As String)
      l1% = Len(A)
      l2% = Len(B)
      C = Space$(l1% + l2% + 1)
      Sh% = 0
      i1% = l1%
      i2% = l2%
      i3% = l1% + l2% + 1
      Do
           If (i1% < 1) And (i2% < 1) Then
              Mid$(C, i3%, 1) = CStr(Sh%)
              Exit Do
           End If
           If i1% < 1 Then
              s1% = 0
           Else
              s1% = Val(Mid$(A, i1%, 1))
           End If
           If i2% < 1 Then
              s2% = 0
           Else
              s2% = Val(Mid$(B, i2%, 1))
           End If
           s% = s1% + s2% + Sh%
           If s% > 10 Then
              s% = s% - 10
              Sh% = 1
           Else
              Sh% = 0
           End If
           Mid$(C, i3%, 1) = CStr(s%)
           i1% = i1% - 1
           i2% = i2% - 1
           i3% = i3% - 1
     Loop
     
     For i% = 1 To Len(C)
         If Mid$(C, i%, 1) <> " " And Mid$(C, i%, 1) <> "0" Then
            C = Mid$(C, i%)
            Exit For
         End If
     Next
     
End Sub
 
Sub start()
 
    LongAdd "12673627632462347623783", "1823975837488346534651111", R$
 
    Debug.Print R$
 
 
End Sub