thanx buddy for quick reply,

now i am explaning you the whole scenario.what i have done is ,i have a sample form with collection_select on it with multiple true(suppose five values).on submit selected values goes into database(suppose two) coreesponding to particular id.now when i again open the page i want the values from database comes as selected(two values that are coming from database as highlighted or selected).and thanx for all your help till now and in future.