concatenating staggered columns - vba

Question

I am working on a macro to loop through staggered columns of strings and concatenate them. Basically data gets added into the columns over time so I need to make it "future-proof". At the moment it picks up all of column H and I but only the first value of J and K. Not sure why it works for half but not the other. I am thinking its to do with my .End(xldown) as i am used to using rows.end(xlup).count to loop through things, but never when it is part of the range?
Here is my code:
Sub Concatenation_for_the_nation()
Range("H2").End(xlDown).Select
For i = 1 To ActiveCell.Row
Range("H" & i).Select
StrStrONE = StrStrONE & " " & Selection
Next i
Cells(1, 1).Select
Range("I2").End(xlDown).Select
For j = 1 To ActiveCell.Row
Range("I" & j).Select
StrStrTWO = StrStrTWO & " " & Selection
Next j
Cells(1, 1).Select
Range("J2").End(xlDown).Select
For k = 1 To ActiveCell.Row
Range("J" & k).Select
StrStrTHREE = StrStrTHREE & " " & Selection
Next k
Cells(1, 1).Select
Range("K2").End(xlDown).Select
For l = 1 To ActiveCell.Row
Range("K" & l).Select
StrStrFOUR = StrStrFOUR & " " & Selection
Next l
Cells(1, 1).Select
Cells(21, 21) = StrStrONE & StrStrTWO & StrStrTHREE & StrStrFOUR
Cells(20, 20) = "Jeff"
MsgBox "steve the pirate"
End Sub

Answer 1

You're repeating the same logic multiple times, so it makes sense to pull it out into a separate Sub.
Tested:
Sub Concatenation_for_the_nation()
Dim c As Range, s As String, sht As Worksheet
Set sht = ActiveSheet
For Each c In sht.Range("H1:K1")
s = s & ColumnString(c)
Next c
sht.Cells(21, 21).Value = s
sht.Cells(20, 20).Value = "Jeff"
MsgBox "arrrrr"
End Sub
Function ColumnString(cStart As Range, Optional sep As String = " ")
Dim rng As Range, c As Range, rv As String
Set rng = cStart.Parent.Range(cStart, _
cStart.Parent.Cells(Rows.Count, cStart.Column).End(xlUp))
For Each c In rng.Cells
rv = rv & sep & c.Value
Next c
ColumnString = rv
End Function