Custom Validator call in ASP.Net

[Mark]

Hi - I have a javascript function which checks if a date (day, month,
year) is valid.

If not (ie. 30 Feb 2003), it changes the day until it is an accepted
date.

Now on my form, I want to create a date range:

tbDay1, tbMonth1, tbYear1 - tbDay2, tbMonth2, tbYear3

I have a custom validator which calls this:

function isvaliddate(source, arguments)
{
syear=document.getElementById("tbYear1");
smonth=document.getElementById("tMonth1");
sday=document.getElementById("tbDay1");
...