SUM cells based on criteria

[sabi.kiss]

I would need a bit of help here.
Take ROW 1 as the 26 pay periods of the year. Each pay period is a fortnight, dates situated in ROW 2. From ROW 3 down we've got the actual hours worked by my employees.
What I'm after is, when I write the pay period number in the criteria cell, it matches with the dates for that particular pay period and SUMs the hours up.

Thanks in advance.
Sabi

 

[Andrew Poulsom]

Let's say the pay periods are in the range B1:AA1, the hours worked are in B3:AA10 and the pay period you want to sum is in A11. In some other cell enter:

=SUM(INDEX(B3:AA10,,MATCH(A11,B1:AA1,FALSE)))

 

[sabi.kiss]

I have to be probably more specific.
ROW 2 has the dates of the specific pay period, for example PP02 is in between 27.6.11 and 10.7.11. ROW 1 has merged cells covering the dates specific to this pay period. So, cell B1 covers cells B3:O3 (a full fortnight). The hours worked are in ROW 3 downwards, depending on how many employees I've got on the list. Criteria for SUMing up the particular fortnight is according to the PP chosen.
ROW 1 has got all 26 pay periods of the financial year.
For each employee I've got their working hours for the whole financial year.
Unfortunately I can't upload a sheet, because I don't know how.
See if this was more specific than the previous message.
Thanks a lot for your help.
Sabi

 

[Andrew Poulsom]

Modify to suit:

=SUM(INDEX(B3:AN10,,MATCH(A11,B1:AN1,FALSE)):INDEX(B3:AN10,,MATCH(A11,B1:AN1,FALSE)+13))

 

[sabi.kiss]

Perfect..thanks a lot for your help. Much appreciated.