VBA Function Composite Score Needs To Be Completed?

I am trying to come up with a composite score that if a child takes a particular course and has a grade then make a composite score. Here is an example below.

ABCDEFGHIJK1Math CourseScience CourseReading CourseWriting Course 
MathScienceReadingWriting Composite Score Looking for2APGEAPAP A+BC-B- 11003

In the example below I am looking for a composite score of 1100. Here is how I derived at it!
=4*100 + 3.2 * 50 + 2.4 * 100 + 3.0 * 100 = 1100

Code:
Function composite(r As Range, course As Range) As String
Dim d As Double
Dim score As Double

[Code]....