sum up specific values

[mmea]

Hi I have a dataset like this

Test place	Number of people	Days of waiting time	Group
A	121343	0	ONE
B	212	1	ONE
C	3434	1	TWO
D	45656	1	TWO

I need to sum up the number of people:

1. if JUST ONLY 1 test place has 0 days of waiting time, then all number of people in that group has 0 days of waiting time --> so in this case test place A has 0 days, therefor I need a new variable that has sum up number of people of A and B, as they are in same group.

2. If NO test places has 0 days of waiting time (as for C and D) then the new variable should sum up the number of people here.

make sense?

Bare in mind I have severel types of groups, and test places

output

test place	Number of people	Days of waiting time	Group	Sum0
A	121343	0	ONE	121555
B	212	1	ONE
C	3434	1	TWO		49090
D	45656	1	TWO