Sort Lookup field by frequency of usage when table is in another application

Sort Lookup field by frequency of usage when table is in another application

I have a list of items in App1,->Form1->TextField1, w/ an additional number field "Count" which will ideally collect the number of times each item in TextField1 is used in App2->Form2->Lookup. I think I know how to sort the Lookup in App2 once I have the Count field populated in App1. How do I get the count from App2-Form2-Lookup passed back to App1-Form1-Count? Also, I'd want the count updated on form submission of App2. So when a new record is created in App2, the count of App1-Form1-Count updates. Does that make sense? Thanks!