Changing Design Modification - Look-up

Changing Design Modification - Look-up

I currently have relationship established between two tables Table A (Parent) & Table B (Child)......the relationship is set-up so that if I delete a record in my parent table (table A)....all related child records (table b) will be deleted....I would like to change the set-up so that the child records in table B will not be deleted....if I delete a related parent record.....Is it possible to change this setting? Or is it to late?

Thank you