function minplu2(callingForm, callingElement, y, feld) { 
  var x = 0; 
  if ( document.forms[callingForm].elements[feld].value == "-" ) 
    x = -1; 
  else 
    x = eval( document.forms[callingForm].elements[feld].value ); 
    
  var result = x + y;
  if ( result < 0 ) 
    document.forms[callingForm].elements[feld].value = "-";    
  else
    document.forms[callingForm].elements[feld].value = result;
}