>>When accessing an object (e.g. a checkbox) on a page in a page frame, it seems that when the object loses focus, this error occurs i.e "Unknown member xxxx" where xxxx is the control name. This seems to happen to label controls as well.
>>
>>Any one has any idea what the problem is ?
>Destine,
>
>What code is running when this error occurs? You can see the code by choosing Suspend from the error message and opening the debugger trace window.

First check the code as Jim suggests. However, in your valid or lostfocus or other method do you have a reference to this object? You must get your hierarchy correct or you will get the 'Unknown Member...' error message

Thisform.ThisPageFrame.ThisPage.MyObject

Or, if you're referring to another object:

This.parent.OtherObject

HTH
Barbara