Week Number Of The Current Month

Hello everyone.

I would like to ask for help on my current problem.

I need to input a date on a text box and another text box say txtweeknumber should determine the week number the date falls on the current month.

for example:

May 1, 2005 should fall on week 1 and txtboxweeknumber should say Week 1
May 9, 2005 should fall on week 2 and txtboxweeknumber should say Week 2
May 17, 2005 should fall on week 3 and txtboxweeknumber should say Week 3
May 25, 2005 should fall on week 4 and txtboxweeknumber should say Week 4
May 30, 2005 should fall on week 5 and txtboxweeknumber should say Week 5

Same goes for all months.
Is there a function to determine which week number of the current month the input date falls?

Please help.

Thanks,

Edwin