VBA code, Error problems

[ZerØ Coder]

Hey there, I have written a bit of code for a coursework task.
but I'm having a problem in it throwing up the right error message.

Private Sub Form_BeforeUpdate(Cancel As Integer)

Dim MsgBoxTxt As String
Dim Places As String

Places = DCount("*", "Booking", "[Course ID] = ComboCourseID")

If DCount("*", "Booking", "[Course ID]=ComboCourseID") < 20 Then

MsgBoxTxt = "Course is Booked with " & Places & " Customers and there are " & 20 - Places & " places left."

Else
MsgBoxTxt = "Course is full with " & Places & " places taken out of 20. Sorry, this booking cannot be made."
DoCmd.DoMenuItem acFormBar, acEditMenu, acUndo, , acMenuVer70

End If

If DCount("*", "Booking", "[Course ID]=ComboCourseID and [Customer ID] = FormCustomerID") >= 1 Then
MsgBoxTxt = "Customer has already booked on this course"
DoCmd.DoMenuItem acFormBar, acEditMenu, acUndo, , acMenuVer70
End If

MsgBox MsgBoxTxt
DoCmd.DoMenuItem acFormBar, acEditMenu, acUndo, , acMenuVer70


End Sub



The error message it is showing at the moment is underlined but the one it should be showing is in bold

I would much appreciate it if someone could get back to me with an answer thank you!