Ssrs 2008 tablix visibility problem

In a new SSRS 2008 report, I am having a problem with a parameter that I call 'SReport'. I basically wanted selected tablixes to display based upon what is selected in this parameter. I basically want either:

  1. all reports, or 2. locator or 3. Cover letter tablix to display.

I have declared the data type as Text and I want to allow Multiple values.

Here is the sql for the dataset called Selreport that is accessed:

BEGIN
SELECT 'Locator' AS rptName, 1 AS rptValue
UNION
SELECT 'Cover letter', 2
ORDER BY rptValue
END

The availalble values are dataset=Selreport, value field=rptValue, label field = rptname.

The default values are dataset = Selreport and value field = rptName.

The visibility on the Locator tablix is =iif(InStr(join(Parameters!report.Value, ","), 1) > 0, False, True) and this works.

The visibility on the other tablix for Cover Letter is =iif(InStr(join(Parameters!report.Value, ","), 2) > 0, False, True) and this is not working.

Thus would you tell me what I can do for the visibility on the other tablix for Cover Letter is =iif(InStr(join(Parameters!report.Value, ","), 2) > 0, False, True) to work?