Formula for record to add above another record in another field

[IDOWU_FAITH_ANU]

I had a client that wanted 4 field

1. field two fields should be able to subtract each other automatically
2. The result of the two fields should be recorded in another field
3. The recorded field should be recorded in another field but it should be a record above each other

[Bill_French]

This is the reason user-defined formulas should be made possible using the underlying SDK/scripts as the runner. Imagine if anything the scripting environment could do was identifiable as a custom formula.