Why Doesn't SELECT @columns... Work?

Bob writes "Your FAQ asks an intersting question:

Why doesn't SELECT @columns FROM @tablname work?

No answer is provided however.

I need to write a stored procedure the passes in a fieldname, retrives next key type int data from that field, increments the field, and returns the NextKey.

Would be nice if something like this worked:
DECLARE @iNext INT
SELECT @iNext = SELECT @columnName FROM Next_Keys WHERE ID = 1
SELECT @iNext = @iNext +1
UPDATE Next_Keys Set @columnName = @iNext WHERE ID = 1
RETURN @iNext

SQL Server 2000 - Win Server 2003
Editing SP from VS2005
TSQL newbe writing first sp"