Help needed in making CGPA calculator

Hi guys, I want to make a CGPA calculator n um facing great difficulties in it!
First off all waat I need is:
When I enter grade in grade column, its grade points automatically comes in points column.. Like I enter A then in the next column its point comes automatically, e.g 4.
N I want to enter grades semester wise, every semester has its own GPA n also a cumulative GPA of all semesters(begin from first date)
Here are the 2 examples of wat I want to do in a proper way! Thanks
Cgpa Calculator.xls

Cgpa Calculator (2).xls

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