Double tap vs single tap a key

[bacon]

I'd like to create a macro that does one thing if I single press a keyboard key and another if a double press. So if I map the macro to the insert key and press it once it sends the F1 key and if I tap the insert key twice with in a .4 millisecond time range it sends the F2. Any suggestions how to accomplish this? I've tried several different programs and haven't found one that works.