SQL server reporting services: how to stop a report firing when opened

I found that I had to set at least one of the report parameters to not have a default to keep the report from autorunning.

I had to use this configuration (notice that all 3 of the parameters I left without defaults accept Nulls so the users can just click the Null checkboxes):

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to get the users to see this and to keep the report from autorunning:

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I set the default value of one of my parameter selections to a value of -1 which does not exist (not a valid parameter value). This did not generate an error. It simply set the parameter drop down box to and prevented the report from running. I couldn't use a default value of NULL because NULL selects everything, and I wanted the user to purposefully make the selection of ALL (NULL) before the report runs. It takes several minutes for the report to render if ALL is selected.

I have done that by changing my query slighlty to require parameters when it is run.

I have then after I have published the report on the report site, specified that the parameter, should prompt the user. This does have the effect that the report does not pull the sql server to its knees when users just open the report to see.