My alts use the following for spells:

/cast [exists,harm,nodead] <spell>
/stopmacro [exists,harm,nodead]
/assist party1
/cast [exists,harm,nodead] <spell>

And this works fine, does what its supposed to do. Which is they attack my target, but if I switch targets they continue attacking the original. However I have one issue I want to be able to reset their main target, so if I switch targets I want to be able to selectively tell them to switch too. Any ideas?