You'd use the keys on the 2 forms to run an append query...
Code:
sub btnCopy_click()
Docmd.openQuery "qaCopyData"
end sub
The query would use the key on the form as the source ,but user must enter the key from the target.
there could be any # of forms open so the app would not know which to use,so the user should enter the target key by hand.
the query will ask for the target id as a param.....
insert into table (ID, field2) select [Enter Target ID] , field2 from table where [id] = forms!myForm!txtID