Yes, this should be possible although at the same it could lead to odd results if there are other populated input elements on the site that aren't URL related.
If you open the Project Properties dialog and select the Custom Attributes category, this has an area where you can enter custom xpath expressions to match attribute or element values.
I did a quick test and I believe that if you add //input[@type='text'][@disabled][@value]/@value to the expression list, this will do what you need. If you aren't familiar with xpath, this will basically look for any input element that has a type attribute with the value text and also has value and disabled attributes.
Hope this helps, if not please let me know.
Edit: Updated to include the final /@value otherwise it would return the element instead of the attribute.