I've been racking my brain trying to figure out how to search for a specific
attribute, and if it meets a certain condition, change it's value.

For example, the following element <item> has several attributes:

<item id="111" name="test" qty="2" price="99.99">

My condition is as follows:
-If the id attribute = 111 then change the qty attribute to 3.

Can this be done, if so, how?

Thanks in advance,