array formula or sumif or sumproduct

[methody]

Hello
In column A I have sales figures. The range is named 'sales'. In column 2 I have postcodes. The range is named 'post'. I am trying to find a formula which will add all the sales which have a post code of BT5 or BT6 or BT7. I thought it was an array formula but I cant get it to work. The formula tried was:

SUM((sales)*(OR(postcode="bt5",postcode="bt6",postcode="bt7")))

I have the curly brackets entered threough 'control-shift-enter'. Is the OR a problem or brackets or should I be using a different formula?

 

[Aladin Akyurek]

=SUMPRODUCT(--ISNUMBER(MATCH(post,X2:X4,0)),sales)

where X2:X4 houses the criteria BT5, BT6, and BT7.

 

[methody]

Thank you very much. That works perfectly for what I asked you. The only wee problem I have is that sometimes the sale has no post code and it throws the formulas out. The range 'postcode' is dynamic and will have the same cells in it as sales even if there is no post code.
Any thoughts

 

[Aladin Akyurek]

Thank you very much. That works perfectly for what I asked you. The only wee problem I have is that sometimes the sale has no post code and it throws the formulas out. The range 'postcode' is dynamic and will have the same cells in it as sales even if there is no post code.
Any thoughts

What does "sometimes the sale has no post code and it throws the formulas out" mean?

 

[methody]

Sorry I had made a mistake with naming my ranges.
Thnaks for your help