ADD ITEMS TO DROPDOWN BOX FROM A TEXT FIELD(USER ENTERS THE ITEM) AND BOUND VALUE ALSO

I WANT TO ADD ITEMS  THE DROPDOWN BOX FROM THE TEXT FIELD(ITEM NAME) WHERE USER ENTER'S THE ITEM DESCRIPTION

AND BOUND VALUE ALSO SHOULD BE ADDED TO THE SAME ITEM.

SAME WAY REMOVE ITEMS FROM DROPDOWN BOX

PLEASE GIVE SAMPLE FORM OR JAVASCRIPT FOR THE ABOVE SCENARIO.....

INDEED HELPFUL FOR MY PROJECT PLEASE SEND ATTACHED PDF FORM