What exactly are the requirements for the UDF?

Right now, the SerialTime() UDF is designed to convert times into seconds (milliseconds) since midnight. Therefore, it doesn't care about dates.

Anyway, since I already have a SerialTime() and SerialDate() UDF, I will think about writing a new DateMath() wrapping function that correctly does date/time calculations.

It might take me a while since I decided to post my login script including all UDFs for everybody's perusal. So, that'll keep me busy for the next day or two.

Stay tuned!