Your indicator source will be normal (planned on today or something similar), your job is where you make this happen. Set the relative end to a negative number.
-3 months would look forward 3 months from now. Just be sure to recollect this frequently (daily) since that will reflect changing plans. Every time you recollect, you'll be getting the latest plans. If you are looking to benchmark (e.g., hours planned next quarter), it gets a little more complicated with the source since you are not collecting in the future but collecting today looking at the current plan for the future).
