Keeping the row the same but changing the column when dragging a formula down

Hi all,

I have a workbook that looks something like:
Worksheet 1

User Jan Feb Mar Apr etc

A
B
C

etc

Worksheet 2

Date User 1 Name User 2 Name User 3 name etc

01/01/11
02/01/11
03/01/11
etc

Essentially a user enters their holidays by putting '1's next to the date they would like to take off in Worksheet 2. Worksheet 1 would total the number of days off in any given month. I've done this by using

=SUMPRODUCT((Holidays!$A$3:$A$368>=DATEVALUE("01/01/2012"))*(Holidays!$A$3:$A$368<=DATEVALUE("31/01/2012")),Holidays!B$3:B$368)

Where Holidays!$A$3:$A$368 contains the dates and Holidays!B$3:B$368 is that users column.
When I try and copy this down the worksheet I would like the B to update to column C and so on. I've tried using INDIRECT or INDEX but can't seem to get them to work. Is it possible to it with one of these? If so, how? Should I be looking at a different approach?

I've seen similar issues posted on here before but its the merging it with my current formula I'm having real difficulty with.

Thanks

It will be easier if you attach the workbook.

See attached.

Note I've had to change the cells B1:M1 to dates, formatted with 'mmm' to look how they did previously.

Hi,

I've opened this and had a look but I'm just getting a seried of #NAME? errors.

Hmm, I really don't know why that would be; I've just reopened it via the attachment and it's working fine for me.