How to show the calculted fields in form in a reports(MS access)?

How to show the calculted fields in form in a reports(MS access)? The datasheet of the form shows different values than the datasheet of the table. Are they not interlinked. If i change a vlue in table it should reflect in the form and vice versa. I’ve used expressions in some fields of a form. But the values are not reflected in the table whereas it is in the datasheet of the form. Please help.