You mean say you want to save only Textbox text details in customerchoice&description table?
If yes then
1) Add the Text box in model popup
2) Use any unique id bases on which you want to save details in customerchoice&description table. so you can use Hidden field and sets its value on click of button when you are opening the model popup.
3) Add the Save Button on Modal Popup and click on the save button sets get the textbox value and pass it to method which call save method using Jquery Ajax call.