The number 1 below is in cell A1 and the number 10 is in cell B1.
I will enter in cell C1 a value from 1 to 6 and in cell D1 there should be a formula that adds rows 1 until the value inputed in C1. The formula sould look at column A and see if the value is less than or equal to value in C1, if so then it should add value in B1, this process should continue for range A1:B6.
Another way, is to have B1 as starting celll, and in C1 enter how many rows down we want sum. Example, if C1 reads 4 then it would sum B1:B4.