Needing some help with passing unsubmitted values

[c-o-d-e]

I'm not sure about this. Here goes;

I have a form, which has.. Category, Subcategory list menu's.

I also have a query, which is suppose to get the value from Category list menu.

To do this, it'd mean passing it through without submitting the form. I have read that this is impossible to do with PHP. As the file is coded in PHP.

 

I have read that it can be done using AJAX. I have never used Ajax, and don't have the time to study it right now.

 

Could anyone help me out at all? it'll probably require alot of help.