I have a problem with a userform. This userform is shown when the user clicks
on a button in the excel spreadsheet. The user is then to enter some info in
various fields in the userForm. However when the user submits erronous info
the program gives a message in a message box to the user. when the user
clicks the ok button the user shall return to the userform (preferably
containing the same info as before). My problem is that I dont know how to
retun to the userform. In the code for Sheet1 I have:

Public Sub startKnapp_Click()
userForm1.Show
End Sub

when the user clicks the button the userform is shown and it is possible to
enter info. The check for error info (it works) is:

Private Sub checkDate()
If (Not (IsDate(userForm1.TextBox1.Text))) Then
MsgBox ("Error")
End If
If (Not (IsDate(userForm1.TextBox2.Text))) Then
MsgBox ("Error")
End If
End Sub

however this sub is called when the user has enterd info and THEN PRESSES AN
OK BUTTON. The code is:

Private Sub genereraRapportKnapp_Click()
Call checkDate
Call mainProgram
Unload Me
End Sub

How do I write the code so that the user returns to the form? I have tried
calling the sub that shows the userform but it does not work (the program
says that it is already shown..). If you know how to solve this problem or
avoid it please help me! Any assistance is of value!