To compute the number of days between two dates, subtract them.
Get ( CurrentDate ) - ETD
will return the number of days from the date in ETD to the current date.
(Date fields store an integer that represents the number of days from 12/31/0000 to the date shown in the field and that's why we can sometimes treat date fields just like number fields.)
Sorry I was unclear with what I was trying to describe. Here is an example:
ETD is 9/23 and the day I entered info in the field is 8/22. He wants ETD to change to red on 9/1, 9/11, and 9/21. If on 9/3 someone changes the ETD to a later date in September, then filemaker will start counting again from 9/3 making ETD change to red on 9/13 and 9/23.
Is what I want to do even possible?
Yes this is possible and I was waiting for a bit more detail before answering more than your specific question. It's important that these be actual dates and not text fields with just the month and day specified but what you want can be set up.
Not Mod ( Get ( CurrentDate ) - YourTable::ETD ; 10 )
will work as your conditional format expression to specify a format change on every 10th day in the interval between the computer's date in its system clock and the date recorded in ETD.
(Mod is simply a function that divides the first term by the second and returns the remainder. Remember your school days trudging through long division computing a quotient and a remainder? It will return zero in this example every time the number of elapsed days is a multiple of 10. The Not operator then reverses the logic so that a result of 0 evaluates as True instead of False.)
Thank you so much for your help and explanation!