Formatting a cell specifically by date

Hi,

I really need your help. I have a worksheet about our daily hotel customer. There are check in and check out dates in every column. We want to create a housekeeping check list in order to follow room maintenance report.

To explain what I need, I want to tell you an example:
For example, guest check in date is 5/12/2011 and check out date 9/12/2011
In another column or worksheet, an "X" will be entered automatically "in a one-day interval"

I mean, another worksheet will include symbolical dates (like 1, 2, 3...) or real dates, and the automation will put an X to the cells at interval:

Since the guest will be at hotel between 5/12/2011 and 9/12/2011, then

dates:
5
6 X
7
8 X
9

6 and 8 must have an X

Thank you in advance