Creating A Gantt Chart In Excel

Hi all,

So, I'm creating a gantt chart in Excel and it's going OK. The formula I'm using is:

=IF(AND(C$1>=$A$2,C$1<$B$2),"1","")

C1 is January 1st, D1 is February the 1st, etc. A2 is the start date of the project and B2 is the end date. Conditional formatting changes the cell with "1" into green. This is working fine except where a project starts mid month the formula does not pick it up.

Can anyone suggest what changes I need to make so that the formula will put a "1" where a project starts mid-month.

TIA,

SamuelT