If I understand correctly:

Code:
F1:
/cast [target=party1, nodead] lesser healing wave
/stopmacro
/cast [target=party2,nodead] lesser healing wave
F2:
/cast [target=party1, nodead] lesser healing wave
/stopmacro
/cast [target=party3,nodead] lesser healing wave

etc
just add your modifiers. It will try to heal party1 first, if dead it goes to the next part.

A point of concern though, unless you are 7ft tall, or use a really small keyboard, hitting ctrl/alt f1 -f5 is going to be extremely difficult to press when you need healing quickly, while still maining DPS or tanking. Have you considered using the num pad?