Select Alternating Columns With Unknown End Point

I was unable to attach my current spreadsheet because it is too large, but I made a simple workbook with 2 sheets, labeled "Before" and "After".

You will see that the only difference between the two is that the second sheet has a few columns selected. I do not need to do any more than simple select them (activate them), because once they are selected I will be able to do what I need to do.

This sample only has information to column L, but the info could in fact go 100's of columns further than column L, so that is why I need to be able to find the last column. But as you can see, none of my rows have information in every cell from A to L, so I need some other way of searching for the last column other than by a row.

That is why I suggested that there might be some sort of macro that can search based on an entire column, and if any data exists in any row of the column, then that would be my last column. (If searching from right to left.) I just can't find this anywhere.

Hope that explains my problem more clearly.

Thanks!