Using Variables In An Update Statement

Declare @vname varchar(4)

select @vname = 'MT1'

--This works fine
UPDATE tblTmpLA
SET MT1 = 2222 / 1000
FROM tblTmpLA
WHERE ID = 1


This is the way I want to do it but

UPDATE tblTmpLA
SET @vname = 2222 / 1000
FROM tblTmpLA
WHERE ID = 1


I get the error that
Disallowed implicit conversion from datatype 'int' to datatype 'varchar'
I guess that the variable does not compile as the text that it holds or so it seems.

I want to put this code inside a WHILE loop where the @vname will change on each iteration.

Any ideas?