SSRS parenthesis around negative values

Group, Still new to SSRS and expressions... however, this should be an easy one I would think. I have a column that is formated as a percent.  Some values are negative -.56% .  All I want to do is put () around anything that comes up negative (.56%).  I guess that is the accounting format for negatives.

I tried =iif(Fields!PercentValue.Value <0, "("+Fields!PercentValue.Value+")")

maybe something with =format(

Thanks in advance for assistance.