Make sure that 'hold_date' in SQL Server accepts NULLs

Insert INTO remotehistory (ordernum, custnum, hold_date, address) ;
   VALUES (Changed.order, changed.custnum, IIF(EMPTY(changed.hold_date), NULL, changed.hold_date), changed_address>)

>We have the following code that inserts records into a remote sql Server 2005 table. However it fails, I think, because the hold_date might be empty.
>
>Insert INTO remotehistory (;
>ordernum, custnum, hold_date, address;
>VALUES (;
>Changed.order, changed.custnum, changed.hold_date, changed_address;
>)
>
>If that's the case, how do I code that so if there is no hold_date the insert works?
>If that's not the case, what else could my problem be?
>Many thanks.