You need to define a named range in the workbook. Go to the worksheet and select the cell that has the report filter (value) that you want to leverage as a parameter. Then go into the Formula tab in the Ribbon and in the Defined Names section
use the Define Name to create a named range at the workbook level that you will then be able to select in the Parameter section in the Excel Services deployment options.
Here are a couple of examples that talk about this: