I'm trying to model patient flow delays through a receptionist and a nurse to
see a doctor. I've got a two dimentional array, with the distribution of
delays created by a receptionist across the top, and those created by nursing
preparation down the side. In each cell, I have the percentage of patients
experiencing that combination of delays, kind of like this:

Receptionist Causes
2min 3min 4min 5min 6min
N 4min 2% 3% 6%
u 6min 8% 11%
r 8min 5%
s
etc.

The patient doesn't care (rightfully) whether the delay is created by the
receptionist or the nurse so I want to create an output histogram showing the
SUM of the two delays. Two patients wait eight minutes, but one delay was
caused mostly by the receptionist, and the other mostly by the nurse. He
doesn't care. I want to create a histogram from this table showing the
percentage of patients experiencing each level of total delay.

Then, I can go back and design process changes or staffing changes to reduce
those delays in a predictable way. Also, I can use the output as input for
queueing models at the next step (say, the doc, the lab, x-ray, an expensive
piece of equipment, etc.)

I've tried using SUMIF kinds of approaches, but have failed. I'm a VERY
novice VBA writer, so any help would be appreciated.

Thanks in advance.