Combining formulas: V-lookup and large numbers

Afternoon guys,

At the moment the work book I am using is fairly huge and things are getting more and more complicated. At the moment I am using two sheets:

The GRADE SHEET: where the students actual grade is inputted
The POINT SHEET: where I turn the grade into a numerical value, as I need to work out the student's best 8 point results.

What I would like to do is combine the following formulas, so I can remove the extra point sheet:

=IFERROR(VLOOKUP(Grades!B2,LOOKUP!$A$1:$B$23,2),"") - turns the grade into a number

=SUM(LARGE(B2:K2,{1,2,3,4,5,6,7,8})) - this then adds up the best eight points.

Any ideas would be greatfully appreciated.

Thanks