Option Explicit

Sub CleanAll()
    Dim rng As Range

    For Each rng In Sheets("Sheet1").Range("A1:A15").Cells 'adjust sheetname and range accordingly
        rng.Value = AlphaNumericOnly(rng.Value)
    Next
End Sub
Function AlphaNumericOnly(strSource As String) As String
    Dim i As Integer
    Dim strResult As String

    For i = 1 To Len(strSource)
        Select Case Asc(Mid(strSource, i, 1))
            Case 48 To 57, 65 To 90, 97 To 122: 'include 32 if you want to include space
                strResult = strResult & Mid(strSource, i, 1)
        End Select
    Next
    AlphaNumericOnly = strResult
End Function