Web Forms :: Button Linking With A Dropdownlist?

i have three fields in a table (1 row, 3 columns)

first cell: "surgeries"

second cell: dropdownlist (with all type of surgeries)

third cell: add_new_surgery Button

the result in my page is this:

surgeries: / dropdownlist (with all types of surgeries) / add_new_surgery Button

i want this:

surgeries: / dropdownlist (with all types of surgeries) / add_new_surgery Button / NEW dropdownlist (with all type of surgeries)

my problem is :

when i click the Button , i want a new dropdownlist to appear in order to insert an additional surgery.