That's the problem, VictorN: writing to an Edit Box, whether it's a CString or a control member, work fine from within the Dialog, i.e in *Dlg.cpp . But the various modules in different cpp files, whilst they can be invoked from the Dlg, cannot access the Edit Box. How can I get a handle on the Dlg from a function which has been triggered from the Dlg, and which is in a separate source file ? The dialog "knows" the executing function, but the function does not know the object which triggered it.