IIf in Query question

I am attempting to execute the following query but am getting syntax errors.
I don't have a lot of practice with the IIf function, need help.
Any Ideas??

--QUERY--
UPDATE View_Data SET
Num_07 = Num_01/IIf(Den_01=0,1,Den_01)
where Data_Set_ID = 444

--Error--
Server: Msg 170, Level 15, State 1, Line 2
Line 2: Incorrect syntax near '='.

More Info
----------------
The fields Num_07,Num_01, Den_01 are all of type 'float'I think that you need to replace the Jet/VB Iif() (http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vblr7/html/vafctiif.asp) with the SQL Server CASE (http://msdn.microsoft.com/library/default.asp?url=/library/en-us/tsqlref/ts_ca-co_5t9v.asp) statement.

-PatP