Macro cell references

I'm needing to add cell references going down a column.

For instance
=b1+b2
=b3+b4
=b5+b6


Is there a quick way to do this? When you create the first 2 cells, and click the little black dot and drag down, it doesn't work. It adds
=b1+b2
=b2+b3

I need it to add 1,2 and 3,4 and 5,6 not 1,2 2,3 3,4.

Is there a quick way?

Thanks ever so much!!