I am trying to write a macro that will do the following as long as there is
data in column A.

Range("F4").Select
ActiveCell.FormulaR1C1 _
= "=IF(LEN(R4C1)<LEN(R4C5),
CONCATENATE(R4C1,R4C5),CONCATENATE(R1C5,R1C1))"
With Selection.Interior
.ColorIndex = 38
.Pattern = xlSolid
.PatternColorIndex = xlAutomatic
Selection.Locked = True
End With

How do I write a Loop that will keep doing this on each successive row until
the cell in column A is blank?