Bring Current Date In Text Box?

I am currently working on a calendar memo site for university, and I'm having a small problem. I have some code to validate a date put into a TextBox (day of month only. Month and Year are in drop down menus and are working fine), but whenever I try to click to validate it, I get the following error in Firebug:

QuotedayBox is not defined

And it points me towards the first part of my validation function. The code to get the TextBox displayed is in a Form HTML element and is:


<INPUT TYPE="text" NAME="dayBox" VALUE="date" SIZE="2">

The validation function is:

function validate(calEvent) {
Step 1: Check box is not empty.
if (dayBox.length = "") {
alert("Please enter a date")

[Code]....

The error occurs on the line "if (dayBox.length = "") {", right at the start of the function. It looks like the validate function is not recognising that there is a TextBox in the form called dayBox, but I can't see why.