Use Range Of Selected Cells As Relative Reference

I have a data that is split into multiple cells and needs to concatenated. Unfortunately, the number of columns wherein lies the data varies throughout the workbook. As such, I wanted to select a range of cells, define this range as the reference point for the macro, run the macro, then move on (selecting a different number of columns on the next try).

For example, I have this:

A
B
C
D
E

1

No
Not Very Far

[Code] .....

I want to select cells A1:B1, run a macro concatenated the two columns, then select cells C1:E and run the same macro to get this:

A
B

1
No
Not Very Far

[Code] ........

So far, I have this:

Code:
ActiveCell.Columns("A:A").EntireColumn.Select
Selection.Insert Shift:=xlToRight, CopyOrigin:=xlFormatFromLeftOrAbove
ActiveCell.Offset(5, 0).Range("A1").Select
ActiveCell.FormulaR1C1 = "=CONCATENATE(RC[1],RC[2])" '