Greetings

I have an array formula that I have entered (using CTRL+SHIFT+ENTER)
as follows:

=IF(CONCATENATE($C$2:$C$1900,$D$2:$D$1900)=$A2,VAL UE(I$2:I$1900),NA())

This works fine on the first row I entered it into and gives a result.
However, when I copy it down so it references A3, A4 etc, it always
returns #N/A for every subsequent row.

Possibly useful other information:
1. The numbers in column I are formatted as text, hence the VALUE
function.
2. Thinking the CONCATENATE might be the problem I created another
column with the concatenated result and referenced that instead, but
to no avail.

Any ideas why it doesn't work?

Thanks

Murray