Here is my array:
Col A Col B
Row 1 M 1
Row 2 M 2
Row 3 M 3
Row 4 N 4
Row 5 N 5

Not sure if the title of my question is correct, but I think I need to use
the VLookup function...I need to achieve the following for a dataset:
Assuming that Column A has a set of some text or codes (in my example just
two--"M" and "N"), and Column B has a set of corresponding numbers, I need to
have a formula (in another worksheet), that totals all values from one code.
for example, to total all rows where the row code is "M", the answer to the
formula would be "6" (1+2+3), and all rows where the code "N" exists, that
answer would yield the number/value of "9" (4+5).

Hope this is clear, and thanks for any help!