OnDrawItem in ZEN dataListBox

I have a dataListBox in ZEN which has an OnDrawItem method associated with it. The DrawItem method never seems to be called and I cannot see why.  I am using IE11. Can anyone suggest a reason? The attached code runs in a namespace called CODE and can be run using view webpage on the TheLabsApp.BioAnal class. Please note that the data is in a global called ^%ANAL that resides in %SYS.