VBA - use a sub or function - vba

Question

I have written a code for a command button in VBA that uses a (column) range as input and has a (column) range as output. I want to use the same code for other command buttons that refer to other columns. I do not want to repeat the entire code, as only the reference to the columns changes.
I cannot figure out how to define this code as a function or sub that I can 'call' in the code for other command buttons which execute the code on columns B, C, D, etc.
This is the code. It removes duplicates and adds the string "rename" to each element of the list:
Private sub rename_column_A_Click()
'copy values of sheet1 column A to active sheet
Range("A1:A30").Value = Worksheets("sheet1").Range("A1:A30").Value
'remove duplicates, keeping first value as column header
Columns("A:A").Select
ActiveSheet.Range("$A$2:$A$30").RemoveDuplicates Columns:=Array(1), _
Header:=xlNo
Range("A" & 2).Select
'add string to each element of list
For i = 2 To 30
If Not Range("A" & i).Value = "" Then
Range("A" & i).Value = "rename " & Range("A" & i).Value
End If
Next i
End Sub

Answer 1

Like John Coleman suggests, you can have your Sub take a Range parameter:
Private Sub rename_column_A_Click()
ProcessRange "A"
End Sub
Private Sub rename_column_B_Click()
ProcessRange "B"
End Sub
Sub ProcessRange(ColAddress As String)
'copy values of sheet1 column A to active sheet
Range(ColAddress & "1:" & ColAddress & "30").Value = Worksheets("sheet1").Range(ColAddress & "1:" & ColAddress & "30").Value
'remove duplicates, keeping first value as column header
ActiveSheet.Range("$" & ColAddress & ":$" & ColAddress & "$30").RemoveDuplicates Columns:=Array(1), Header:=xlNo
'add string to each element of list
For i = 2 To 30
If Not Range(ColAddress & i).Value = "" Then
Range(ColAddress & i).Value = "rename " & Range(ColAddress & i).Value
End If
Next i
End Sub
I removed the two Select lines of code. I don't think you need them.