Remove All fields option from searchbox

Hello I am looking the way to accomplish that the searchbox only perform search by entering a value for specific field PIN.
In catalog-template I have:

{joodb searchbox| PIN}

How can I remove the All fields option from Search box?

This is the link of my project.

demo-hits.com/demo4/index.php/coope-online

Thank you in advance for your help!

It's no problem besause you owe the PRO-Version.
The pro version has a command called SEARCHFIELD

Use {joodb searchfield|PIN}

instead of searchbox!
See
/support/documentation.html?search=searchfield

Thank you! That helped me to reduce the search to 1 field. My goal is that the searchfield returned just the PIN number that is typed.

Something like this:

SELECT * FROM TABLE1

WHERE searchfield entry = PIN

I want to avoid that by leaving the searchfield in blank or just typing 1 or 2 digits of the PIN (PIN consist in 8 digits) returns any row.

I tried the SQL-WHERE Expression option included in the menu by adding PIN = PIN but do not work.

Please take a look here:

demo-hits.com/demo4/index.php/coope-online

Thank you in advance for all your help.