Need to Sum based on Combobox field selection

I am new so any help would be really appreciated. I have created a form that has 13 text boxes and 13 combo boxes. That each user can enter how many hours they were absent. (text box names are text40 text41 text42 text43 etc. Next to each text box is a combo box that has the options of reason for absence the options are Vacation, Sick, Personal, Holiday (Combo box names are cmbobox1 cmbobox2 cmbobox3 cmbobox4 cmbobox5 cmbobox6 etc . Now there is a summary box on the top but i am not sure how to sum for each of the below categories

lets say the following
Date hours (textbox) Explanation of Absence (combobox)
09-01 8 Vacation
09-02 8 Vacation
09-03 5 Vacation
09-04 8 Holiday
09-05 8 Personal
09-06 1 Personal
09-07 7 Sick
09-08 5 Sick

Each of the below has a text box (4 total text boxes ). how would i set up the calculations. If they change The hours do i have on change option?
Vacation Total 21 Text box name : Text11
Holiday Total 8 Text box name: Text12
Personal Total 9 Text box name: Text13
Sick Total 12 Text box name: Text14

I created the form in acrobat professional.

The user is able to put any number of separate explanations for 1 day.