Sage 100

Anyone run into a situation where an end users wants to view the QTY Available in Inventory and only have those Sales Orders due to ship within XX day (say 20 as an example) show in the ON SO field? This probably trickles across a few lookups

Yes. We dealt with it with a customized On Order report.

I'm thinking script - have long term SO use a WHSE 99. Within 20 days of ship date have a script change WHSE from 99 to 00.

Are you thinking have it update the WHSE on the Sales Orders? That should work.

Yes if the open SO gets updated then all QTY on hand warnings would function as normal.