T-SQL Help With Order By

In a stored procedure MS-SQL I am trying to write an order by expression that is a function of the incoming paramters.

SO for example

CREATE PROCEDURE test
@sortby varchar(10)
AS

SELECT * FROM table WHERE condition
ORDER BY @SORTBY

Gives an error (1008) but the error message implies that you can use a variable in the order by expression.

I have tried every combination I can think of

with the variable as varchar = column name, as integer .

I have also tried variations of
Order by COL_Name(OBJECT_ID('item"), variable) and I ether get errors or no errors but no order either.

Any leads appreciated.

TIA

Mike