Sorry, I typed the assignment operator ( = ) instead of the equals operator ( == ).  Corrected code is shown below:

function Main()

{

  var c9 = DTSSource("Col009")

  var c10 = DTSSource("Col010")

  if (c9 == null || c9 == "null")

    c9 = "";

  if (c10 == null || c9 == "null")

    c10 = "";

  DTSDestination("CLO") = c9 + c10;

  return(DTSTransformStat_OK);

}

Mike