Multiple Value Parameters

Hello Everyone,

I'm using a sp to create a report using report builder 3.0. I have start and end dates as parameters. Now i added city as a new parameter. It works fine, but i want it as a drop down selection. In the code  i added the following after the WHERE clause.

AND City IN (@City).

In the report builder in the parameter properties i selected "Allow Multiple Values" and in "Available Value" selected the dataset and select the SP and when i run the report i'm getting the following error

 The report parameter ‘City’ has a DefaultValue or a ValidValue that depends on the report parameter “City”. Forward dependencies are not valid.

How can i select multiple values? Please need help.

Thanks