Calculating a sum (count) and percentage field

[mickeyboy]

I am trying to work out the expression that will first count the number of 'Yes' returns in a series of yes/no boxes and then display as a percentage.

To explain...The yes/no boxes represent attendance over a 20 lesson course. I have added a count for each lesson for student attendance..(grouping them in the footer) but I would like to add the number of attendance for each student.

Any help would be greatly appreciated

 

[Isskint]

in general terms use

Dcount("StudentID","tableattendance","((StudentID=" & LinkField & ") AND (YesNoField = TRUE))")