How do I store a number in excel as Int32?

I have to get numbers from each row in column B of Excel for 3 different sheets and store the sum of them in a var.

For example, Sheet1!B2 is 6, Sheet2!B2 is 9, Sheet3!B2 is 5.
I need to store the sum (20) in another variable. How do I do it?
I had an error that said “Get Row Item: Int32Converter cannot convert from System.Double.”

for Get Row Item output use a variable with type object/double then you use another variable which is int32 and convert and store the fetched value.

Convert.Int32(var_obj.ToString)