Reporting Services :: How To Pass A Blank Parameter

I have 5 Parameters created in my report.

1, 2 and 3 parameter are text inputs. 4th is multi-value parameter and 5th is again a text input. I need to Pass a blank parameter to my 5th parameter.

1) I tried the below Expression in the "UploadedEnt" DataSet Properties and not in the "Main" DataSet.

=IIF(Parameters!UploadedEntiParam.Value ="",Nothing,Parameters!UploadedEntParam.Value)

I have taken the actual sql query (file) and I have just placed the select statement.

DataSet Name: UploadedEntselect distinct UploadEnt
from
(
SELECT DISTINCT col1, col2...
....) Ent

Order by 1OR logic has been applied in the Tablix Properties Filters as an expression.=Fields!value1.Value like Parameters!value1Param.Value Or Fields!value2.Value like Parameters!value2Param.Value Or Fields!value3.Value like Parameters!value3Param.Value Or Fields!value4.Value = Parameters!value4Param.Value(0) Or Fields!UploadEnt.Value = Parameters!UploadedEntParam.ValueFilter: Expression = TRUE2) I tried applying NULL check box which works perfectly but I do not want to apply that here.How to Pass a Blank Parameter?