Modify a Group of fixtures


I have a group of fixtures (6 desk chan) and in my second cue in my first cuelist I record this group with a intensity of 30%.

Well, now in this cue, I want to change the group... I don't want to have my 6 desk chan, but just the 3 first. So I modify My group... But in the cue all the 6 fixtures stay with the intensity.

And I don't have just a cue with this 6 fixtures, but 80. And I don't want to re-program all the 80 cue...

What's the solution ?