Wildcard Searches

I have a number of functions that require the input of parameters in order to ultimatly create a report under Reporting Services by making use of a Stored Procedure.

All the functions etc work as does the stored procedure, but it only works if I specify data that I know exists e.g.

DECLARE @return_value int

EXEC @return_value = [dbo].[spWTRalldatareportsummary]

@dt_src_date = N'04/28/2006',

@chr_div = N'NE',

@vch_portfolio_no = 3,

@vch_prop_cat = N'core'

SELECT 'Return Value' = @return_value

GO

How can I set this so that it will wild card the value. For example rather than having to specify

@chr_div = N'NE', I could specify something like

@chr_div = N *, so it would show both NE and SW values in the result set.

Anybody point me in a direction here. I have tried % but that does not seem to work, I get a

Msg 102, Level 15, State 1, Line 7

Incorrect syntax near '%'.

Thank in Advance