Merge two sets of data

[999Dom999]

I have two sets of data on one worksheet say first is col A:B then second D:E and I want to merge them summing the value if one account is in both sets in G:H


FIRST:

Acc No Value
100001 200
100020 100
103003 200
102030 500

SECOND:

Acc No Value
100001 400
100020 250
170300 200
160000 500
180000 100
190000 100

I want to merge them so I get:

Acc No Value
100001 600
100020 350
103003 200
102030 500
170300 200
160000 500
180000 100
190000 100

Any ideas please, formula or macro would be good thanks.

 

[999Dom999]

Gets pretty busy this forum, anyone had a chance to have a look at the above?

Many thanks for any help.