If user types in a wrong value, then an error message pops up

I have an array of Languages in: Range("C1:C100")

The user types in a language in cell: "J4" then click NEXT BUTTON (runs a macro)
If what he typed in does not match a language in the array, then an error message pops up saying: "That language is not supported. Please correct the language to continue."

Here's the code where the error message needs to be added:

Sub Step4()
    Dim i As Long
    Dim strAddress As String
    For i = 1 To 2
        strAddress = Choose(i, "G4", "J4")
        If Len(Trim(Range(strAddress).Value)) = 0 Then
            Range(strAddress).Select
            MsgBox "Please enter " & Choose(i, "the quantity of your order.", "the language of your order.")
            Exit Sub
        End If
    Next i
    Range("J4") = StrConv(Range("J4"), vbProperCase)
    Sheets("StatusAnnual").Range("Z1:AQ7").ClearContents
    Sheets("Image Catalog").Activate
    Range("DI11:DI25").Copy
    Range("CH47").Select
        Selection.PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks _
        :=False, Transpose:=False
    Range("A87").Select
End Sub

Thanks!

Why don't you use data validation for this?

Select your cell on column J and go to Data, data validation, on allow choose list and then choose your Range("C1:C100"). It should limit the possible values of the cell.

Great that works too..

Now I just thought of something else.... since it's the type of (dropmenu) that can be typed in. Is there a way it can correct the spelling or guide the person as he's typing it in...

For example as soon as he types in "Eng" the rest of it is suggested as "English" ... kind of like how search engines work today...?

English is just an example... but I'm talking about doing so for all the available languages????