Error: no data exchange control with ID 0x03F4. what does it mean?

I am afraid I can't do much unless I see the actual code, otherwise it will just be posting on posting and nothing will be solved. :(

There are several reasons for dialog data exchange to fail. So far your answers did not provide enough information to draw any intelligent conclusion.

One of the most common errors is to add and delete variable without deleting entries in DoDataExchange. That is true if entries were created by the wizard.

Another common mistake is to create DDX calls for the control that is not a child window of the window where DDX is used.

Third: you insert member variable of the window type and create control by explicitly calling Create member.