Thanks Igor,

The fact that breakpoint appears inactive, and loading dll does not result in breakpoint hit makes me think that you have attached to process other than the one that actually loads your DLL. It's very unlikely that your CAD somehow prevents debugger from normal working.
When I run CAD tool it doesn't load automatically my .DLL. The linking process is executed when in the CAD (already running) I do some particular procedure called "design elaboration" (I won't go into details what it is). Probably (sorry again) during this procedure the initial CAD tool runs some other module and "this other module" links my .DLL. But Ok, I'll try your proposition concerning InitInstance.

as the latter blocks thread normal execution while DllMain must never be blocked.
Beside the dubugging issue, should I reject "DoModal approach" in favour of one, based on Create function ?