user-signup and dynamic values

Hi yea,
I would be grateful for any input. 

in the email templates i have templates like USER-SIGNUP1, USER-SIGNUP2 etc etc and they all work when I assign the value directly in the websitemembership page. 

How can I best assign a dynamic value to USER-SIGNUP, 

'template_id' => 'USER-SIGNUP2',    <<< this works this is in the websitemembership page 

= emailTemplate_loadFromDB(array(
//'template_id' => 'USER-SIGNUP2',
'template_id' => USER-SIGNUP . $_REQUEST['countrylang'],        <<<< this does not work

I have added a hiddenfield to the signup form area in itself with a dynamic value in it. when the form is submitted I had thought that USER-SIGNUP . $_REQUEST['countrylang'], would have given me the desired effect

thanks for any help

kenny