Conditional formatting not working

[Pat]

I have a sub form that contains one control for date and another invisible for number of days. The number of days is used for conditional formatting of the date field.
I run the subform by itself and the conditional formatting doesn't work.
I have included the definition of the conditional formatting, can you see what's wrong?

ConFormDatesAvail.png

[Pat]

I have found the problem, i didn't need the table identifier in front of the DaysToColour.