The short answer is you can't.  Not really.

There are two basic approaches to handling this kind of scenario, though.  The first is to create a group based on whichever field you are using to suppress, and put the chart in the group header.  This is particularly useful when your parameter is used to select a single value to filter your report (e.g., sales for one region, or for one salesman).  Then, the chart only reports on data for that group, which should give you the slice you want.

If you have a more complex scenario, however, that solution won't work.  In that case, you will want to create a formula for each of the values that you want to appear on your chart.  The formula should be a fairly straightforward IF..THEN..ELSE structure.  IF (criteria to appear in the report) THEN (value to be charted) ELSE (0 if numeric, "" if string).  When you run the chart, this lumps all the suppressed data together into either one group, or ignores it if you are summing the values.  However, do note that zero values can still appear on the chart.  A TopN sorting may help you here.

Out of curiosity, why are you using parameters to suppress data, rather than putting them in the select criteria to actually restrict the data returned?  In the long run, that's probably the preferred solution.