Sub Total in ALV

Dear all,

Suppose I have the following data in an internal table:

Inv No.     Date        Customer   Pack  Load No.  Tax Amt
9000000001  01.01.2007  ABCABCABC    24  1190020    100000
9000000001  01.01.2007  ABCABCABC    24  1190021    100000
9000000001  01.01.2007  ABCABCABC    24  1190031    100000
9000000002  11.01.2007  ABCABCABC    35  1190881    300000
9000000002  11.01.2007  ABCABCABC    35  1190882    300000
9000000002  11.01.2007  ABCABCABC    36  1190991    300000
9000000002  11.01.2007  ABCABCABC    36  1190992    300000
9000000002  11.01.2007  ABCABCABC    36  1190993    300000

How do I make the list look like below in ALV. I'm using FM REUSE_ALV_GRID_DISPLAY.

Inv No.     Date        Customer   Pack  Load No.  Tax Amt
9000000001  01.01.2007  ABCABCABC    24  1190020    100000
                                         1190021          
                                         1190031          
Subtotal                             24             100000
9000000002  11.01.2007  ABCABCABC    35  1190881    300000
                                         1190882          
                                     36  1190991          
                                         1190992          
                                         1190993          
Subtotal                             71             300000

Thanks in advance.

Regards,

Goh Tiam Tjai