Calculating GPA for random number of subjects for differnt students

Hi,
I want to calculate the point average marks of specified subjects for differnt students.(Attached)
GP= Grade point
Cr=No of Credtis

Point average= sum(GP*Cr)/ Sum(Cr)
One is illustrated in AA 15. But that formula is not quite comfortable as I hv to mannually enter each column for GP & Cr for differnet subjects.

Specified number of subjects vary from one student to another one.
Since, we hv subject codes,(ME3307,ME4310,etc...) is there easy method fo solving this out.?
Many thanks!

Hi Dim,

Just need small clarity.

How can we identify as which subject eligible for which student?

Thanks

Hi Adhawan06,
It is decided by the teacher and has to be entered manually.
Thanks!