strSuche = "*" & replace(txtSuche.Text, " ", "*") & "*"
strPart1 = "(Stamm LIKE " & strSuche & " AND Beschreibung LIKE " & strSuche & _
  ")"
strPart2 = "(Stamm LIKE " & strSuche & " AND Kürzel  LIKE " & strSuche & ")"
strPart3 = "(Beschreibung LIKE " & strSuche & " AND Kürzel LIKE " & strSuche & _
  ")"
 
Set rs = db.OpenRecordset("SELECT * FROM Aufgabe WHERE " & strPart1 & " OR " & _
  strPart2 & " OR " & strPart3)