Why does a Combobox inside a messge box works for first time but not all the time?

Hi all,

In my application, I have a 'simulate'  button  which shows a message box with a combobox inside it when it is clicked for the first time.

I want this to happen everytime ,when the button is clicked.But the problem is, If I want to press the button one more time then I get  an error like this:

"Uncaught Error: The object with ID droplist was destroyed and cannot be used anymore."

Why do I get this error?

Can Someone help me with this?

Here's what I have tried:

View code:

Message was edited by: Ramya A.R I have attached the screenshot of my message box.