SSRS datasets filter from a parameter

Hello this is my first attempt using a filter and a parameter.

Based on the value of the parameter, I want to bring back records that are either = 0 or >= 0.  Here is my datasets filter:

here is my parameter MTCActive:

Label................Value
Active Only......O
All........................A

here is my filter that does not work.

=IIF (Parameters!MTCActive.Value = "O", Fields!TotMTCHrs.Value > 0,Fields!TotMTCHrs.Value >= 0) 

Can you tell me what is wrong with it?  Thanks