as deguix suggested, i've began writting an header-file, containing as much ready-to-use functions from the windows-api as possible.
the point is, to give the user e.g. this syntax:
${AnimateWindow} $HWND "500" "${AW_SHOW}|${AW_SLIDE}" "r0"instead of this:System::Call 'user32::AnimateWindow(i $HWND, i "500", i "${AW_SHOW}|${AW_SLIDE}") i .r0'