Conditional Calculations for radio buttons

Hi,

I have a list of 8 courses each with a radio box (Yes and No) to tick, Yes is set to 0.25 and no is set to 0.  I then have a text box with a calculation to add these up so if all yes boxes are ticked the total is 2.  How do I make this so the total will only be 8 if ALL yes boxes are ticked, if any of the No boxes are ticked the total will be 0.

My radio boxes are Qualification1, Qualification2, Qualification3, Qualification4, Qualification5, Qualification6, Qualification7 and Qualification8.  And my text box for the total is called "Total for Qualifications Q24".

Thank you