Increase in Value, Circular Reference Issue

The problem I am having feels like a simple one that I can only see a very complicated solution to. So hopefully someone else can come up with an easy way to resolve this.

I have 3 cells, an initial amount (A2), the new amount (B2) and the increase value (C2).

Cell A2 always stays the same, 100.
Cell B2 needs to increase by the amount in C2.
Cell C2 is a random number between 1 and 20.

What currently happens is when I refresh the random number, I get this happening:
Refresh 1: 100 105 5
Refresh 2: 100 111 11
Refresh 3: 100 102 2
Refresh 4: 100 113 13

What I want to happen is this:
Refresh 1: 100 105 5
Refresh 2: 100 116 11
Refresh 3: 100 118 2
Refresh 4: 100 131 13

I want the Value in B2 to increase with each refresh, rather than replace. Anyone have any ideas?

((Currently having issues uploading a practice sheet and will upload one asap, for now the 3 formulas from the cells are simply: (A2 100 (B2 =A2+C2 (C2 =RANDBETWEEN(1,20).))

Do you need it in only 1 row? If so, you'll need VBA to solve this.

Otherwise, perhaps consider this layout instead.

Row\Col	A	B	C	D
1		Initial number	New amount	Increase value
2	Refresh 1	100	106	6
3	Refresh 2		109	3
4	Refresh 3		128	19
5	Refresh 4		133	5
6	…

where...
C2: = B2 + D2
C3: = C2 + D3
D2:D5 = RANDBETWEEN(1,20)