Где ошибка

Private Sub Command1_Click()
Dim q As Integer
Dim s As String
Dim i As Integer
 
os = ""
Dim st As Integer
q = Val(InputBox("Введите основание системы счисления"))
If (q < 2 And q > 9) Then
MsgBox ("Основание системы счисления должно быть от 2 до 9")
Return
End If
s = InputBox("Введите число в системе счисления с основанием " & q)
For i = 1 To Len(s)
If (Val(Mid(s, i, 1)) >= q Or (Val(Mid(s, i, 1)) = 0 And Mid(s, i, 1) <> "0")) Then
MsgBox ("Число введено не правильно")
Return
End If
Next
 
For i = Len(s) To 1 Step -1
os = Mid(s, i, 1)
st = Len(s) - i
rez = 0 + os * q ^ st
Next
MsgBox ("Результат " & rez)
End
End Sub

Private Sub Command1_Click()
    Dim q As Integer
    Dim s As String
    Dim i As Integer
    Dim rez As Integer
    Dim z As Integer
     
    os = ""
    Dim st As Integer
    q = Val(InputBox("Ââåäèòå îñíîâàíèå ñèñòåìû ñ÷èñëåíèÿ"))
    If (q < 2 And q > 9) Then
        MsgBox ("Îñíîâàíèå ñèñòåìû ñ÷èñëåíèÿ äîëæíî áûòü îò 2 äî 9")
        Exit Sub
    End If
    s = InputBox("Ââåäèòå ÷èñëî â ñèñòåìå ñ÷èñëåíèÿ ñ îñíîâàíèåì " & q)
    For i = 1 To Len(s)
    If (Val(Mid(s, i, 1)) >= q Or (Val(Mid(s, i, 1)) = 0 And Mid(s, i, 1) <> "0")) Then
        MsgBox ("×èñëî ââåäåíî íå ïðàâèëüíî")
        Exit Sub
    End If
    Next
    For i = Len(s) To 1 Step -1
        os = Mid(s, i, 1)
        st = Len(s) - i
        rez = rez + CInt(os) * q ^ st
    Next
    MsgBox ("Ðåçóëüòàò " & CStr(rez))
    Close
End Sub

Private Function NOD(x As Integer, y As Integer) As Integer
If (x <> 0) Then
   NOD = NOD(y Mod x, x)
Else
   NOD = y
End Function
Private Sub Command1_Click()
Dim m As Integer, n As Integer, p As Integer, q As Integer
m = Str(Text1.Text)
n = Str(Text2.Text)
Do Until (m > 0) And (n > 0)
q = NOD(m, n)
p = m / q
q = n / q
Loop
MsgBox "Результат: " + Str(p) + Str(q)
End Sub

Private Function NOD(x As Integer, y As Integer) As Integer
    If (x <> 0) Then
       NOD = NOD(y Mod x, x)
    Else
       NOD = y
    End If
End Function
 
Private Sub Command1_Click()
    Dim m As Integer, n As Integer, p As Integer, q As Integer
    m = Str(Text1.Text)
    n = Str(Text2.Text)
    q = NOD(m, n)
    p = m / q
    q = n / q
    MsgBox "Ðåçóëüòàò: " + Str(p) + Str(q)
End Sub