Excel - Sum Formula

Hi Experts

I am trying to write the SUM Formula inside the excel sheet in such a manner that I do not have to manually enter the Cell Range for which the SUM has to be done. Instead I have a column in which cell range are given already, I want the formula to pick up the cell range from there itself.

I am not being able to figure out, how to write this formula. Can someone please suggest a solution ?

And also please mention if I can reuse this solution multiple times in the same formula or not, in case I need to pick up 2 or more cell ranges inside one single Sum Formula.

I have attached the Excel File having the data and I have explained the formula requirements inside it, with comments.

SUM-Formula.xlsx

I am using the following software versions -
Microsoft SQL Server Management Studio version-  12.0.2000.8,
Microsoft Office 2016 x64
and Windows 7 x64

Thanks for any help

Thanks