Private Const Digits As String = "NZP"

Private Sub Command1_Click()
Dim var1 As Long
Dim var2 As String

On Error GoTo ErrorHandler

var1 = Val(Text1.Text)
Do While Abs(var1) > 0
    Select Case var1 Mod 3
    Case 0
        var2 = Mid(Digits, 2, 1) & var2
        var1 = var1 \ 3
    Case -2, 1
        var2 = Mid(Digits, 3, 1) & var2
        var1 = (var1 - 1) \ 3
    Case -1, 2
        var2 = Mid(Digits, 1, 1) & var2
        var1 = (var1 + 1) \ 3
    End Select
Loop
If Len(var2) = 0 Then var2 = Mid(Digits, 2, 1)
Label1.Caption = var2
Done:
Exit Sub

ErrorHandler:
Label1.Caption = "Error"
Resume Done
End Sub

Private Sub Command2_Click()
Unload Me
End Sub

Private Sub Text1_KeyPress(KeyAscii As Integer)
If KeyAscii = 13 Then
    Call Command1_Click
End If
End Sub