Code wont run from sub form

[Michael]

I have a button on each record of a sub form. The code in the on click
event is very simple for now it just says

msgbox "testme"

but I get this error when I run it.

"This error occurs when an event has failed to run because Microsoft
Office Access cannot evaluate the location of the logic for the event.
For example, if the OnOpen property of a form is set to =[Field], this
error occurs because Access expects a macro or event name to run when
the event is fired."

The on click field in the properites says [Event Proceedure] like all
the others.

Is there something about this being on an unbound sub form that is
causing this problem?

Any other ideas?