Combo box requirement

[jeo]

I have 2 cascading combo boxes on Form1. After I select one things out of dropdown0 and then select another thing out of dropdown2, I click on a button that opens another form - Form2- depending on values selected from both of those comobo boxes. That works good. What happens is when I come back to Form1 and select something out of dropdown0, but nothing out of dropdown2, it lets me proceed to opening Form2 and it keeps the value from dropdown2 from previous time.
What I need is to make Selection out of the second drop down mandatory. Right now I have a little msgbox in the After-Update event on dropdown0, but that's not enough.
Any ideas how I can make it so it doesn't let you proceed to Form2 if dropwdown2 is null?
Thanks.

 

[Mile-O]

Use the AfterUpdate event of the first combo to set the second's value to Null.

 

[jeo]

Thanks! That worked great.