I have a table (Multi-Page as Tabs) named 'bncit_01a_le' and I want if the value of the field 'Source' (select) change to 1 then the second YUI-Tab should be removed.

I put this javascript code to ClientScript => Table-Specific -> Add/Copy page -> Startup Script

===
$("#x_Source").change(function() {
if (this.value == "1") {
bncit_01a_le_add.tabView.removeTab(bncit_01a_le_add.get('tab_bncit_01a_le2'));
}

});

Does not work. What is wrong?

Google "twitter bootstrap remove tab" for more information.

You may use jquery .hide() to hide the tab. View the html source to find out the href value for the different tab for your table and try the following code to hide the tab:
// your condition
// to hide tab
$("[href='#tab_cars3']").hide(); // if href value is #tab_cars3