Javascript date validation

Hello smart people!

I set up a form that acquires d.o.b. information with three separate fields, but I’m not quite sure how to validate them. Please help.

The html part that contains the input fields looks like this:

Birthday:<br />
<input type="text" name="monthOfBirth" size=2" maxlength="2" value="mm" />&ndash;
<input type="text" name="dayOfBirth" size="2" maxlength="2" value="dd" />&ndash;&nbsp;
19<input type="text" name="yearOfBirth" size="2" maxlength="2" value="yy" /></font></b>

so i have three fields:
one for the month
one for the day
and one for the last two #s of the year

How do I use javascript to validate these fields?

I just want to check that the month field is made up of a number from 01 to 12;
day is from 01 to 31
year is 00 to 99

Please help!