using instance variable within JavaScript function loaded in a partial

Im wondering, how do I go about allowing my javascript function to load the updated instance variable that is loaded within a partial? To be specific, I have a javascript function call: onmousedown="changeTab(this)" for a tab in my layout. This function passes an instance variable with an Ajax.Request like so:

changeTab(tab) { new Ajax.Request( '/test/ajax', {parameters: { date: <%= array_or_string_for_javascript(@date) %> }) }

@date is changed each time a different link_to_remote is called and the link_to_remote catches this change and send the updated @date variable, but my javascript function changeTab does not pass the updated @date variable. How do I get the changeTab javascript function to pass the new updated @date variable?

This code is only evaluated once so what happens is normal. One way of doing things is to have the date be a parameter of changeTab (assuming that whatever calls changeTab is updated after these requests). Another is to have your requests update some global javascript variable