Add New Item In Bounded Combobox?

i have two tables. i bound one combo linked to another table value.

my problem is if user wants to add new value to combo how can i add that value to my combo as well as new row to table...

for example :

table 1:
PID,ItemID,Price

table 2:
ItemID,ItemName

i create form for create and modify table1. and i put combo in my form cmbItems for list of all items.

cmbItems.DisplayMember = ItemName
cmbItems.ValueMember = ItemID.

now if user want to add a new item in this form what should i do... and new item should be added in database also....