If you just need it for display purposes, enter layout mode and place the layout text: @@ where you want to see this number.
Thanks, you've been really helpful out there.
Though. I put @@ as you said. And. It never restarts numbering once the month changes. So in that setting, Only birthday in April is #1, then, only birthday in June is #2, while it should be #1, because it's a separate month, and 3 birthdays in september are #3, #4, and #5, while they should be #1, #2 and #3. Is there a way to fix it?
Oops, that method only numbers from top to bottom, it doesn't start over.
Here's a method that will start over with each subset by month:
Define a new SubSummary field that computes the "count of" any field in your table that's never blank such as your month field. Select the running count option, Restart summary for each sorted group and select your Month field as the "when sorted by" field.
You can then place this field in your layout to see a number that starts over with each month.
works like charm, case closed :) thank you very much!