If you can use table buffering you should be able to use tableupdate in a transaction and rollback if either fails to be updated.

cursorsetprop("buffering",5,"Header")
cursorsetprop("buffering",5,"Detail")

loop Start

Insert into Header..
Insert into Detail..
Begin Transaction
if !tableupdate(0,.t.,"Header") .or. !tableupdate(0,.t.,"Detail")
	*!* Transaction failed
	Rollback
	messagebox("Update failed")
else
	end transaction
endif
....
.....
loop end