Getting the list to show the selections will be a little trickier. You will need to start by creating a new array of the values stored in that column. You can use the explode function like this to do that:
$your_array_var = explode(", ", $row_YourRS['PropertyType']);
Once you do this you will then need to loop over this array for each entry in the list and compare the value of the option with values in this array. If the values match then you will need to add the selected="selected" attribute to that option.
This is a little custom and will require hand coding the loop and comparison.