Create Macro to adjust channel intensity parameter across cue list.

I am programing the same show for two different stages. Because the stages are slightly different, I would like to be able to build a macro that will modify the intensity parameter on a specific channel throughout an entire show.

CHANNELS 4 & 5 are at 80% intensity or higher in an number of cues spread throughout a cue list. I want to program a macro to knock CHANNELS 4 & 5 down to 50% across any cue that  they are at 80%. If Channel 4 & 5 are below 80%, then it would leave CHANNELS 4 & 5 alone. Is this possible?

Thanks for any help!