How do I return a null value for a negative number in my statement below

[hcsavage]

if(is_null(${orders.need_by_date}),diff_days(${orders.created_date},${receipts.receipt_created_date}),diff_days(${orders.need_by_date},${receipts.receipt_created_date}))

[jcdufault]

Hi hcsavage, 

You need to wrap your whole statement in an if( <<whole statement» <0, null, <<whole statement>>)

if(if(is_null(${orders.need_by_date}),diff_days(${orders.created_date},${receipts.receipt_created_date}),diff_days(${orders.need_by_date},${receipts.receipt_created_date}))<0,null,if(is_null(${orders.need_by_date}),diff_days(${orders.created_date},${receipts.receipt_created_date}),diff_days(${orders.need_by_date},${receipts.receipt_created_date})))