IFF systax help please

Is this works in SSRS? If need to put an expression in TextBox

My requirement is like 

IF Field value A = USA then SUM(Field B) - SUM( Field C )

Else

Field E - SUM(Field C)

=IFF((Fields!Engtype_CD.Value)="PTM" OR (Fields!Engtype_CD.Value)="TM", SUM(Fields!Projected_Revenue.Value)-SUM(Fields!Projected_Cost.Value),(Fields!Enagagement_Plan_Net_Rev_amt.Value)-SUM(Fields!Projected_Cost.Value))

Is IIF works with my requirement ?

Appreciate inputs on this.

Thanks,

Kp