Function to select just letters in a cell?

Public Function exdata(s As String, Optional o As Integer = 0) As Variant
Dim a As String, y As Integer

If o = 0 Then
    exdata = s
    Exit Function
End If

For y = 1 To Len(s)
Select Case Asc(Mid(s, y, 1))
    Case 48 To 57
        If o = 1 Or o = 4 Then a = a & Mid(s, y, 1)
    Case 65 To 90, 97 To 122
        If o = 2 Or o = 3 Or o = 4 Then a = a & Mid(s, y, 1)
    Case Else
        If o = 2 Then a = a & Mid(s, y, 1)
End Select
Next y

Select Case o
    Case 1
        exdata = --a
    Case 2 To 4
        exdata = a
End Select
End Function

Function strings(txt As String) As String
With CreateObject("VBScript.RegExp")
    .Pattern = "\d{1,}"
    If .Test(txt) Then
        Set mItem = .Execute(txt)
        For Each m In mItem
            txt = Replace(txt, m, "")
        Next
        strings = txt
    End If
End With
End Function