Excel Macro formula for groups of numbers

I have strings of numbers in a column (n) I need help with a macro that will total the groups with the sum in column (o) right of the last row of the group

172.01
-372.01 Total

172.01
-172.01
-200.00
200.00
0.00
40.00
20.00
-20.00
-20.00
20.00 Tolal

172.01
-172.01
-200.00 Total

172.01 Total

172.01
-172.01
-100.00
150.00
0.00
30.00
20.00 Total