Sum Last Six Numbers With Different Spaces

I have an instance where I have a list of numbers in different rows with different amounts and I want to add up the last 6 numbers, they're all in the same column however they're not all in consecutive rows.

Also, the gaps between the rows is not consistent.

The example below explains what I mean (I've add numbers in between so you can see the varying gaps, but they're actually blank cells)



(B1)ADD ME = 2
(B2)**blank cell**
(B3)**blank cell**
(B4)**blank cell**
(B5)**blank cell**
(B6)ADD ME = 5
(B7)**blank cell**
(B8)**blank cell**
(B9)**blank cell**
(B10)**blank cell**
(B11)**blank cell**
(B12)**blank cell**
(B13)**blank cell**
(B14)**blank cell**.........................