>it’s possible to create a twain source that will open another source installed on my computer?
yeah, you’re just building 2 projects.
>how can I create a valid handle to a window inner this DLL?
create a a native window, use its handle.
but i think you have at least one other largish issue if you follow this design. the driver for your scanner is occationally going to want to display some errors as dialogs that you’ll have to have one of your projects handle. for an example, unplug your device then try to scan with a twain app. I bet you get a dialog – and when your code does the opening part in twain you won’t get a twain return code telling your app that there is a problem until _after_ you click on the dialog. i had a similar situation and ended up using cbtHooks to deal with it, but truthfully its a hassle becasue i have to have info about the dialogs that i want supressed and every once in a while a driver update comes with a slightly different dialog.