Assign Enrollment Numbers to Different Class..

Hello EveryOne!


In my UserForm I have got a ComboBox which have different Classes name( for example Class 1 , Class 2 , Class 3 .........Class 10 )

In the UserForm I have a Text Box to manually assign "Roll Number" to Students.


I used the following code which just look not repeating Roll Number... but it does not look that which class is Selected from comboBox.

Please see attachment that what I really want .....and how roll numbers should be assigned through userform

If WorksheetFunction.CountIf(Sheet1.Range("B2:500"), TextBoxRollNo.Text) <> 0 Then
 MsgBox "This Roll Number has been already used", vbCritical
 Exit Sub
 End If

I will be really thankful If anyone could help me please..

Where is your userform?