Here is what I need the formula to do: I will have two columns, Column A
will have a value and Column B will have a code. I want to Sum the numbers
in Column A IF the Code in Column B has the letter "R" in it. So, using
the data below, my formula would add the values 100+400+500 from column A
and return a result of 1,000. Any help would be appreciated!

Column A Column B
100 R1
200 M3
400 R2
500 R6
700 I1
300 M3