How to acess to property in dataSource?

I use dataSource and dataSource loop to extract data from excel.But I don't want to set property in the configuration grid manually,can I set the property in groovy script just like we use ' xmlholder and setNodeValue' in a soap request? Plus,if I use
"testRunner.runTestStepByName("getExcel")"in the groovy(getExcel is the DataSource),it just extract the first row in the excel,how can i set the "max number of rows to get" to 0 by script.and how can i get the actually rows got in the datasource by script?
Is there anyone can help me? many thanx