How to make total Percentage from textbox and dropdownlist

I have a form with dropdowns and textboxes

I want to get sum of all values of dropdowns and textboxes in percentages but dont know how to  do this, please solve it 

and

when I dont select a value from 1st dropdown(dd1) then I must not select 2nd dropdown(dd2) and 

if didnot select 2nd dropdown(dd2) then I must not select 3rd dropdown(dd3) and so on. I mean for selecting next dropdown, the last value of dropdown must be selected, 

My file is attached please do something urgently, Thanks for cooperation,