// first retrieve the current opportunity record
var opportunity = this.BindingSource.Current as Sage.Entity.Interfaces.IOpportunity;

// now create the code to run the report
// note, I am using placeholders like %MYVALUE% where I will inject the values from my opportunity entity
var reportCode = @"
    var reporting = Sage.Services.getService('ReportingService');
    if (reporting) {
        var pluginId = reporting.getReportId('Opportunity:My Opportunity Report');
        reporting.setReportJob(pluginId, 'OPPORTUNITY', Sage.Utility.getCurrentEntityId());
        reporting.reportJob.rsf = '{OPPORTUNITY.OPPORTUNITYID} = ""' + Sage.Utility.getCurrentEntityId() + '"" and {OPPORTUNITY.SOMEFIELD} = ""%MYVALUE%""';
        reporting._showReport();
    }
    return false;
";

// assign that javascript string to the button and ibject the values into the string as needed
btnTest.OnClientClick = reportCode.Replace("%MYVALUE%", opportunity.SomeField);