how i can add no from listbox if it containing name & value

Question

hi guys can any one help me ..i am developing a project in c# windows form & in that form there is 1 combobox,1 listbox and 1 textbox. my combobox should be containing the data(i.e. service_name) which is fetching from sql database and these service_name is added into the listbox with there service_price (i.e multiple item selected from combobox is added in listbox with there srvice_price) (for ex.shaving=50 in one row) now i want my textbox should be show the addition of all service_price