I'm currently putting together an e-commerce site for one of our companies at work, and in the cart, I have a textbox which has a quantity of that product they chose earlier on.

When you want to update a variable through a textbox by the process of hitting the enter button, what is it...i.e. onClick, onSelect, I just cant think what exactly it is.

Any help would be greatly appreciated.

I assume you mean client side?
If you want to trap an event when the user tabs away (or presses enter) from the textbox then try onBlur .

If you want to capture the textbox value when you process some other event then use something like:

... event processing
var myValue;
var o=MM_findObj('txtboxid');
if (o) { myValue=o.value }
... do something with myValue

Hope this helps
Bob