how to set multiple event on button?

Question

Dear friends
thanx for your kind support on dropdown list issue,
now i need to know can i set 2 event on the 1 button in form?
i mean i have a form with few field and having only one button.
so how can i set that when user select insert option then under this menu this button work for insert function and when user select update option is works update function.
please let me know how to set it
Thanks in advance