Excel VBA - in a list, if cell equals specific value then

Question

I started working on some code, and it works, but I feel like it could be done more effiently. Below is a portion of it to show what I'm doing. To simplify the idea, I've made it here so if the cell in column M is A, B, or C, it puts a 1 in column L. If column M is a D, E, or F, it puts a 2 in column L. And if column M is a G, H, or I, it puts a 3 in column L.

Is there an easier way to do this than how I'm doing it? I'm going to be dealing with a couple hundred possible values. Alex P suggested I build a reference table. I've never done that before, so I'm not sure if that's my best bet or not.

Sub ChangeTest()
 Dim LastRow As Long
 Dim i As Long
 LastRow = Range("M" & Rows.Count).End(xlUp).Row
 For i = 2 To LastRow
 If Range("M" & i).Value = "A" Or Range("M" & i).Value = "B" Or Range("M" & i).Value = "C" Then
 Range("L" & i).Value = "1"
 End If
 If Range("M" & i).Value = "D" Or Range("M" & i).Value = "E" Or Range("M" & i).Value = "F" Then
 Range("L" & i).Value = "2"
 End If
 If Range("M" & i).Value = "G" Or Range("M" & i).Value = "H" Or Range("M" & i).Value = "I" Then
 Range("L" & i).Value = "3"
 End If
 Next i
End Sub

• Mathieu Guindon: "Simplifying" your code works well for Stack Overflow. On this site however, you'll get much more useful feedback if you include your real, actual, working code. Try it next time! (please don't edit your question in such a way that would invalidate already-given answers) - see a guide to Code Review for Stack Overflow users for more information.
• Robby: I posted this on Stack Overflow first, and I was told to post it here. And I got a site warning for pasting my real, actual, working code because it said most of my post was code. So I thought because of that, and just so everyone would be able to make more sense out of it, I made it much simpler and shorter.
• Mathieu Guindon: SO folks were right - getting feedback on any/all aspects of your code happens on Code Review, not SO. I've never seen that warning though, but the post length limit on CR is pretty much double that of SO, and you should be fine if your post presents the code to the reviewers, i.e. explains what's going on and why - as you've done here.
• Mathieu Guindon: cross-posted from Stack Overflow

Answer 1

Don't know if it would be faster, but it would look cleaner to use a Select.

Sub ChangeTest()
 Dim LastRow As Long
 Dim i As Long
 LastRow = Range("M" & Rows.Count).End(xlUp).Row
 For i = 2 To LastRow
 Select Case Range("M" & i)
 Case "A", "B", "C"
 Range("L" & i) = "1"
 Case "D","E","F"
 Range("L" & i) = "2"
 Case "G","H","I"
 Range("L" & i) = "3"
 End Select
 Next i
End Sub

• Robby: This looks good. There's going to be lots of cases, so I'm hoping this isn't too slow. It might take me a few days to fully implement.
• Rdster: At least this way, it is much faster to add a new condition rather than using it in an IF.
• Rdster: @Robby - If this helped, please mark as the answer.
• Robby: I haven't been able to implement it yet. Sorry. I'm out of the office for a few days.