Generating A URL Based On Two Drop Down Box Selections?

I have a javascript function that will load a CSV file in to a grid:

Code:

function load(url){
table.setURL(url);
table.request();
}
<button onClick="load('URLTONEWFILE.CSV')">Load New File</button>

This works perfectly, however I need to take it a step further to load CSV files, based on user choices from two drop down boxes. Something like this:

Code:

<form name="myform"">
<select name="mycolour">

[code]....