DLookup statement giving Error message

Access 2003-
I'm currently attempting to use the DLookup() statement on my subform for a text box called 'tbxViewPrice'.  What this statement will do is go to my 'Item' table, find the 'Price' next to the item number (ItemNmbr) and populate the associated price in each text box next to the item shown on the sub form table.  ItemNmbr is an identical name given to the subform table field that is supposed to equal the 'ItemNmbr' field from the 'Item' table (which is why the code looks the way it does below).  When I enter the code from below into the text box control source, all of the values next to each part shows '#Error' in the Price column.  I should probably mention that the 'Item' table is located on our SQL server database, and is not stored locally on my machine.
Thanks,
Ryan

=IIf(IsNull([ItemNmbr]),"",DLookUp("Price","Item","ItemNmbr = " & [ItemNmbr]))

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