If your variables are stored in cells, you can do something like the
following:
1. Assuming the value of mFrow is stored in A1 and the value of mLrow is
stored in A2.
2. In cell A3, write down the following:
=TEXT("H" & A1 & ":H" & A2, "")
3. In cell A4, you can get your sum with the following formula:
=SUM(INDIRECT(A3))
Basically, in cell A3, we are building up the expression "H1:H10" and in
cell A4, we are using the string in A3 to build the range using the
INDIRECT() function.