strAuswAZ = Auswahl_AZ(Index).Caption
Select Case strAuswAZ
    Case "B", "D", "F" To "H", "J" To "N", "P" To "R", "T", "V" To "X", "Z",
"0" To "9"
        strAuswAZ = Left(strAuswAZ, 1)
        strAuswAZ = "Like '" & strAuswAZ & "*'" '"" <---was zuviel 
 
    Case "A"
        strAuswAZ = "Like (""[AÀÁÂÃÄÅ]*"") " <--- wird nicht funzen 
...
sSql = "SELECT tblFirmen.ID, tblFirmen.Firma As Firmenname,
tblFirmen.Str,tblFirmen.Land, tblFirmen.PLZ, tblFirmen.Ort,tblFirmen.KatNr "
& _
         "FROM tblFirmen " & _
         "WHERE ((UCase(tblFirmen.Firma) = " & strAuswAZ & "));" <--- wrong!