Dynamic Login && User Creation

Hello. I'm trying to create a new login and username inside a trigger using variables.

This code works:

create login testUserName with password = 'testPassword'

The problem comes when I try to use variables for the username and password like this.

create login @username with password = @password

Does anybody know how to get around this problem?

BTW, the error message it gives is this, but I really doubt that semicolons have anything to do with it. If I literally type my data in the create login call it works fine, but when I use variables it doesn't.

Msg 102, Level 15, State 1, Line 14

Incorrect syntax near '@username'.

Msg 319, Level 15, State 1, Line 14

Incorrect syntax near the keyword 'with'. If this statement is a common table expression or an xmlnamespaces clause, the previous statement must be terminated with a semicolon.