If I'm understanding your question correctly, Synergy doesn't have macro functionality. By what you've described, that is what your looking for.

The only thing I can think of is something that has macro capability associated with hardware, such as a G15 keyboard. You could write a macro that would do just that, but it would be in the G15 software, not Synergy.

I don't have experience with other hardware besides G15, but I hope this answers your question.