MessageBox changing event processing ?

Hey all..

I am trying to ask a user a question during some event processing, but it seems everytime I pop up the messagebox where a yes/no response is required the event never 'finishes', meaning, if the event code was called when a user clicked on a CheckBox, the checkbox never gets checked, regardless of what the user chooses on the messagebox ...

but, if the code doesn't get to the messagebox call, everything works fine..

Any Help ?

Thank you