How to resolve this in multiple ways

i have a script which has few several buttons. by clicking those buttons it runs .ms files and pre installed macroscript.

        on btn19 pressed do
	filein "scriptsfolder/Delete overlaped objects or"
	on btn9 pressed do
	( "KM-3D.COM Tools" "ConvertToSBObject"

If there is no .ms or macroscript it shows the following error.

So, i need the solution in the following way,

1.How to suppress the error message (shows nothing).

2.How to show a popup message that "script is not available."

3.the button should be disabled if .ms or macroscript is not available.