Nevermind. I figured it out.
I put up a "jump select list" on page to select district. And then filter the recordset with a URL parameter on the UE page.
So coming from the select page with district values in the select list. I get "email.php?distrikt=CBU-1"
And because the recordset in the email.php page is filtered with the URL value. It only sends email to "CBU-1" district in this case.