Settings > Options > Display > Select Client Information and add Locked date to the Display. Move it to the top. Click Ok

Using the Locked date find the 120 and highlight them (Click and use down arrow). Back up those client

Using the Locked date find the 120 and highlight them (Click and use down arrow). Select Client > Unlock Return.

Using the Locked date find the 120 and highlight them (Click and use down arrow). 

Those clients should still be at the top of your listing, highlight them again and proforma. 

Doesn't sound like hours, but still tedious. Alternatively wait for a Lacerte fix in a new update?