Use Replace to convert the target characters (tab, vbCrLf, etc.) into spaces. Then while there are multiple space combinations, use Replace to convert double spaces into single spaces.

Public Function CleanString(strSource As String) As String
    On Error GoTo CleanStringErr

    ' convert tabs to spaces first
    strSource = Replace(strSource, vbTab, " ")

    ' convert all CRLFs to spaces
    strSource = Replace(strSource, vbCrLf, " ")

    ' Find and replace any occurences of multiple spaces
    Do While (InStr(strSource, "  "))
        ' if true, the string still contains double spaces,
        ' replace with single space
        strSource = Replace(strSource, "  ", " ")
    Loop

    ' Remove any leading or training spaces and return
    ' result
    CleanString = Trim(strSource)
    Exit Function

CleanStringErr:
    ' Insert error-handling code here
End Function

Formatted by Neil Crosby