how do I select a column based on condition?

Select
    ordr_num as num,
    ordr_date as date,
    CASE WHEN @status <> 'Cancelled' THEN ordr_ship_with ELSE NULL END as shipwith
From
    order where ordr_num = @ordrNum

SELECT ordr_num as num, ordr_date as date, 
    CASE WHEN @status<>'Cancelled' THEN ordr_ship_with ELSE NULL END as shipwith 
FROM order 
WHERE ordr_num = @ordrNum

Try this out

Select 
    ordr_num as num, 
    ordr_date as date, 
    CASE 
        WHEN @Status <> 'Cancelled' THEN ordr_ship_with 
        ELSE NULL END
    as shipwith 
From order 
where ordr_num = @ordrNum

Although I have a feeling that you STATUS is an actual column in the Order table. In that case, do this:

Select 
    ordr_num as num, 
    ordr_date as date, 
    CASE 
        WHEN Status <> 'Cancelled' THEN ordr_ship_with 
        ELSE NULL END
    as shipwith 
From order 
where ordr_num = @ordrNum