Is bit masking restricted to long or integer type only?

I created a function that determines when events can happen on
several different days based on what day of the week a month begins
and how many days are in the month.
My idea was to assign each date to a bit and when a date was passed to
the function it would use bit masking to return whether the date was
one of the selected dates.
It works until a month with 31 days because 2^31 is larger than a
long.
I tried to use double type and got the overflow error.
I tried to use the CDec conversion but nothing seems to work.

I've searched Google and Deja and I not found a solution
Thanks for any advice
Merlyn