How can I move data from field 1 in table 1 to field 2 in related table 2? Using lookups doesn't seem to do the job except on new records.

Would the Record> Replace Field Contents work for you?

I wouldnt recommend using Replace field contents here.

You can Store it in a variable instead.

Set variable [ $whatever; Table1::Field1 ]

Set Field [ Table1::Field1; "" ] //Clears field because moving data

Go to layout [ Table2 layout ]

Go to record [] //Whatever record you want.

Set field [ Table2::Field2; $whatever ]

If you are trying to change the first related record, then you can just you set field.

Set field [ Table2::Field2; Table1::Field1 ]

Set variable [ $whatever; Table1::Field1 ] //Clears field because moving data

You could also use Go to Related record to show the related records. But without knowing your structure, I cant be more concise.