Month number to Month name

[Ziggy1]

This must be simple but I'm missing something. I have a field that has just a Month number. I want to display the Month name but I am getting the incorrect results. I'm using:

Expr1: Format([monthap],"mmmm")

But it gives me only December for the number 1 and January for all the other numbers.

thanks

 

[Kodo]

monthname(monthnumber)
simple function.

 

[Ziggy1]

Thanks...simple enough