Variable Row # Sums

[King of Ka]

Apologies if this question has been answered before, I haven't had any luck searching. It seems very basic but it's completely stumping me: how do I add a formula which can sum from the cell above it to a point further above, determined based on an adjacent column. So for example:

	A	B
1	Entry 1	5
2	Entry 2	6
3	TOTAL	X
4	Entry 3	12
5	TOTAL	Y

In the above, X should be 11 and Y should be 12. How can I use the same formula in both to get the correct answers?

Thanks!