vba macro to sum by group

[viva0521]

Hey there,

suppose I have a table like this:

V	From	To	index	decision
v1	D1	A1	1	ship
v2	D1	A1	1	ship
v3	D1	A1	1	ship
v4	D2	A2	1	ship
v5	D2	A2	1	ship
v6	D2	A3		no ship
v7	D2	A3		no ship
v8	D3	A3		no ship
v9	D3	A3	1	ship
v10	D3	A3	1	ship

<colgroup><col width="64" span="5" style="width:48pt"> </colgroup><tbody>
</tbody>

how can i create a macro to sum up by group (from, to , index) like following:

V	From	To	index	decision	# of ship
v1	D1	A1	1	ship
v2	D1	A1	1	ship
v3	D1	A1	1	ship	3
v4	D2	A2	1	ship
v5	D2	A2	1	ship	2
v6	D2	A3		no ship
v7	D2	A3		no ship
v8	D3	A3		no ship
v9	D3	A3	1	ship
v10	D3	A3	1	ship	2

<colgroup><col width="64" span="6" style="width:48pt"> </colgroup><tbody>
</tbody>

please advise!
Thanks!