Check out the Send
command in either AutoHotkey_L
Basically you have to make sure the correct window is the Active Window(has keyboard focus) and send it Control-s. AutoIt may be a bit easier to learn for a beginner. AHK_L I think is a bit more powerful. But either can easily do this for a single application. There are forums associated with each language where you can ask for help. They are both free.
edit: I forgot to mention. They both work on XP or newer Windows. For what you are doing it shouldn't matter if the OS is 32 or 64 bit.