Need help combining an IF statement and lookup, choose, or match functions

I've pulled out a sheet from a workbook because the workbook is too large to attach to this forum. In the attached worksheet, I need a formula for the range J6:AM90 and so forth.

What this formula needs to do is pull a value based on what I think is a simple IF statement. I've began to play with a formula and it is located in J6:J90. But it is incomplete and I'll explain why.

My first version of this sheet was simply pulling values from the sheets that matched the value in cells A6:A90 and returned the specific value into cell K7 and so forth. As you can see from looking at the formula in K7:O7, the range of values that I am needing to reference are U4:U33.

Here is what I need a formula to do:

Row 4 dates will most likely replace the day 1 etc. values in row 5 but using it as it is, if an ID admits on May 1, 2013 and checks out May 31, 2013, then it would stand to reason that their 1st day of service wouldn't be till cell U6 and so forth.

Make sense?

That's where the formula will start to populate according to the lookup from the sheet that matches the ID. You'll see my attempt to try that in cell J6. The problem with my formula, is that it will ONLY return the value in U4. It doesn't work then to auto fill throughout the sheet.

I hope this makes sense and is enough info in detail.

Thanks! You guys are awesome!