Fill columns botom up fashion (editing current code)

hey all, I have a piece of code that prompts me to choose which column to be filled bottom up, I would like to modify this and add it in as a macro so that it fills columns H and columns I in a bottom-up fashion

Sub x()
Dim Last As Integer, Dn As Integer, oLt As String
Dim Rng As Range
On Error Resume Next
Set Rng = Application.InputBox(prompt:="Please Any Cell In Column ", Title:="Fill Cells", Type:=8)

Last = Range("a" & Rows.Count).End(xlUp).Row + 1
For Dn = Last To 1 Step -1
    oLt = Cells(Dn, Rng.Column).Value
    
    Do While oLt = Cells(Dn, Rng.Column) Or Cells(Dn, Rng.Column) = ""
               Cells(Dn, Rng.Column) = oLt
                        If Dn = 1 Then Exit Sub
                          Dn = Dn - 1
    Loop
           Dn = Dn + 1
Next Dn
End Sub