参考答案

'正确的程序
Private Sub C1_Click()
    Dim k As Integer
    k = 0
    While Not Op1(k).Value And k < 3
        k = k + 1
    Wend
    If k < 3 Then
        Text1.Text = calculat(Val(Left$(Op1(k).Caption, 2)))
    End If
End Sub
Function calculat(n As Integer)
    Dim k As Integer, t As Long
    t = 1
    For k = 2 To n
        t = t * k
    Next k
    calculat = t
End Function
Private Sub Form_Unload(Cancel As Integer)
    unload_sub
End Sub