Comparing Two Internal Tables with the Same Key

Hello Experts,

I have a problem with Internals tables with the same key. And i have to make out the difference using fields.

For Ex:

     LOOP AT LT1 INTO LS1.

          READ TABLE LT2INTO LS2WITH KEY KEY = LS2-KEY.

         IF sy-subrc EQ 0.

                *comments

          ENDIF.

     ENDLOOP.

Now the real Problem is both table having the same key each and every time, but the fields will be containing different values.

I have to take out the difference from two table and store it into other table.

Ex:

First table LT1:      Key   Field1   Field2    Field3

                              A       1          2           3

First table LT2:      Key   Field1a   Field2a    Field3a

                              A       1            4               1

First table LT3:      Key   Field1   Field1a   Field2    Field2a   Field3     Field3a

                              A                                2            4            3            1

I have to take out the difference from LT1 and LT2 and store it in LT3.

Require Guidance!!!!!