No, I don't think you can do that. Think of what you need to do to change the datasource...
Well, I'll take a step back, it depends on how the data is delivered to the report. If you have separate users and you bind to the data via odbc, you could set each user's odbc connection to a different datasource. If you have 1 user, they would need to change the odbc setting. If you pass the datasource to the report (ADO.net, XML file) then you control the datasource and not Crystal.
But if you want to pass a parameter to change the datasource, the answer, I am fairly sure, is NO.
As stated above, there are ways around this.
HTH