I place a command button in a form, with which I use it to open another form with condition of [ID]=Form![AnotherFormName]![ID]. It runs good when the form works not as subform. But when I click this button when the form works as subform, a dialogue box appear to ask for Parameter. Why it works properly in the main form, but ask for parameter in subform.

Please help! Thanks a lot.

You have to reference the main form and subform ie. Forms!MainFormName!SubformName.Form!Control
HTH

Rich, I appreciate your help very much. Now it works. Thanks a lot!