Excel 2007 Nested IF Formula

Hello All,
I am trying to get a formula in which the results are all dates plus a certain number of days. I am getting an error while trying to add the days. This is the formula

=IF(R3=CECs!,"10+CECs!F3",IF(CECs!R3=CECs!B4,"30+CECs!F3",IF(CECs!R3=CECs!B5,"30+CECs!F3",IF(R3=CECs!B6,"30+CECs!F3",IF(R3=CECs!B7,"30+CECs!F3",IF(R3=CECs!B8,"30+CECs!F3",IF(R3=CECs!B9,"21+CECs!F3",IF(R3=CECs!B10,"AWAITING",IF(R3=CECs!B11,"10+CECs!F3",IF(R3=CECs!B12,"AWAITING",IF(R3=CECs!B13,"80+CECs!F3")))))))))))

If the cell has a value that is equal to a cell in another spreadsheet in the same workbook then it will add a certain number of days to a cell with a date. The bold section is where I am starting to get the error. Here I am trying to add 10 days to a date which is in the cell CECs!F3. Most of the other returns are a certain number of days added to a date value in a specific cell. So again the main problem is how do I add a number of days to a fixed date. I am using Excel 2007 btw. If anyone can help me that would be great I've been trying to figure this out for a week now

Try

=IF(R3=CECs!xx,10+CECs!F3,IF(CECs!R3=CECs!B4,30+CECs!F3,IF(CECs!R3=CECs!B5,30+CECs!F3,IF(R3=CECs!B6,30+CECs!F3,IF(R3=CECs!B7,30+CECs!F3,IF(R3=CECs!B8,30+CECs!F3,IF(R3=CECs!B9,21+CECs!F3,IF(R3=CECs!B10,"AWAITING",IF(R3=CECs!B11,10+CECs!F3,IF(R3=CECs!B12,"AWAITING",IF(R3=CECs!B13,80+CECs!F3)))))))))))

You need to remove the quotes round your addition of days.

Plus error where xx is in formula