Peter,

No you have the idea of transaction wrong. A transaction is used to group a number of table actions into a single all or none operation. Generally when used with buffering all of the inserting and replacing will have all taken place before the transaction starts. The transaction would be soething like this;

 BEGIN TRANSACTION
 llRollBack = .F.
 IF NOT TableUpdate(0,.f.,"Table1")
    llRollBack = .T.
 ELSE
   IF NOT TableUpdate(0,.f.,"Table2")
      llRollback = .F.
   ELSE
      IF NOT TableUpdate(0, .F., "Table3)
         llRollBack = .T.
      ENDIF
   ENDIF
 ENDIF
 IF llRollBack
    ROLLBACK
 ELSE
    ENDTRANSACTION
 ENDIF