Unusual UDF Behaviour

I'm new to UDfs in excel and I've stumbled across this problem a number of times now. When I create a Module containing a function, Excel will refuse to recognize it. It does not populate into the Excel list under 'User Defined Functions' and manually referencing the function anytime before this only results in a return of "#NAME?" to the cell i try to use the function in. Closing Excel and opening it does not do anything and i'm positive I'm calling my function correctly. After a few days of working in the file, Excel decides to acknowledge the functions I created (it will populate in the User Define funciton formula list) and everything will work. Sounds crazy. Is there a step between creating a UDF Module and calling it in your spreadsheet that I'm not aware of? Any thoughts as to what might be causing this?

Are macros enabled when you create the UDF?

yup - macros are enabled.