Access 2002

I have a database to keep track of inventory and inspections. I have a checkbox that if checked another form should open. Everytime I try this I get an error “A problem occurred while Microsoft was communicating with the OLE server or Active x Control. Close the OLE Server and restart it outside of Microsoft Access. Then try the original operation again in Microsoft Access”. What am I doing wrong? What event procedure should I use? Right now I am using Lost Focus butI have also used on click.

TIA