Is there any Macro(e.g PROJECT_EXE)?
If oyu exe is called as your project you could do:
$(PROJECT_DIR)/bin/$(PROJECT_NAME).exe
(That's how I do it, assuming you have a bin folder, too.)
I can't remember if there was also a macro for the executable itself (which would depend on the target then)... (good question, though ;-)) I'll take a look...