convert function from Access SQL to T-SQL 2005

Can someone please convert this access sql function for me to work in t-sql 2005.

I am tring to take the selling price minus the cost as one number. And divide that by the original selling price to produce a second number

Thanks :)

 =IIf([Selling Price]=0,0,([Selling Price]-Nz([Cost]))/[Se开发者_C百科lling Price])

IIRC it should be something along the lines of;

ISNULL((ISNULL([Selling Price],0) - ISNULL(Cost,0)),0) / ISNULL([Selling Price],0) AS Margin

But here I am getting a divide by Zero error.

any suggestions?

SELECT
    CASE 
        WHEN ISNULL([Selling Price],0) = 0 THEN 0
        ELSE ([Selling Price] - ISNULL([Cost],0))/[Selling Price]
    END AS fieldName
FROM TableName

CASE 
   WHEN ISNULL([Selling Price], 0) = 0 THEN 0
   ELSE ([Selling Price] - ISNULL([Cost], 0)) / [Selling Price] 
END