Create a new column with unique account numbers that will be used to reference your list of data.

Create a Max column

Create a Min column

Create a difference column

Using your example:

Find the MAX (Array formula needs to use Ctrl+Shift+Enter to set formula)

=MAX(IF($A$2:$A$46=H2,$C$2

Find the MIN (Array formula needs to use Ctrl+Shift+Enter to set formula)

=MIN(IF($A$2:$A$46=H2,$C$2

Then =Max - Min gives you the score difference...it is all automated based on your data set.

I attached your example data with the solution I noted above.

example.xlsx