Macro to auto select adjacent cell then cell underneath

I have used options to select the cell adjacent rather than underneath when hitting enter.

However, I need this to be the case for column A, but for column B when the user hits enter I would like excel to jump straight bellow in column A.

So they select A1, input data and hit enter- it jumps to B, input data and hit enter- jump to A2.

I have it jumping to B1 but I'm not sure how to make the second jump.

Maybe some sort of event macro..?