If Me.frame1.value= Null then
Msgbox("Select an option")
...it gives me the error (at the second msgbox, the else clause)
Invalid use of null. However, in the first if i checked for null!
The same goes if I change the 'null' in the if to -1.
PS: the value for the frame is read 'on load' from a database field, a field which is empty.
I hope you can help...
Your error is in how you test for nullness ... Change the conditional to:
If isnull(frame1.value) then
Question: Why don't you set the default option of the option group? Something to consider: Every radiobutton is assigned an option value defaulting at 1 and increasing from there (it is overrideable) so having no default selection on startup you could use 0 ...