SQL Hierarchy and Sum on Same Table

[R2d2Rabeau]

Hi,

I am new to T-SQL, I am trying to fill-in a table with data already present in the table. The data to be used is located in type = C
The problem is that the value in Type = B is the the sum of the Values of Type C but ONLY from the following rows AND until another type is encountered.
(for exemple value in id = 2 is only 100 + 105 and in id = 5 it is only 79)
Same principal applies for Type A but with the B values.
The table looks like this:

id type value
1 A NULL
2 B NULL
3 C 100
4 C 105
5 B NULL
6 C 79
7 B NULL
8 C 46
9 C 23
10 C 26
11 A NULL
12 B NULL
13 C 126
14 C 138
15 B NULL
16 C 149

Can someone get me started with a code?
I am stuck...

Thank you for your help,