Crystal Reports Alter sql at runtime

Message

   Im brand new to crystal reports and have some problems.
I have made a report as i like it with subreports and more. Im now ready to fill in the relevant data with where clauses and the likes.

Im just confused about the whole parameter thingy, so im more interested in altering the sql statements on my report at runtime. Is there any way this can be done? Im thinking about something like:

CrystalReport1 report=new CrystalReport();
string sql=report.getSql();
sql+=" where id in (1,2,3)"
report.setSql(sql);
report.ReportSource=report;

I just dont seem to be able to find the methods to do this.