what's get_random() anyway ? to generate a random number you have to use Math.Random() ... unless you created a function to do this and named it get_random(), but as you didn't post them I have to ask
then, you don't use sound[whichsound] again in the toast, you first call the function and assign the result to a variable, which already contains the filename. Something like this:
code:
var fileName = getaSound();
MsgPlus.DisplayToastContact(Messenger.MyName , "Has Just Opened A Window With" , Contact.Name , fileName);
Remember, the files must be in your script's directory. If you have them in a subdirectory like "sounds", you have to use:
code:
MsgPlus.DisplayToastContact(Messenger.MyName , "Has Just Opened A Window With" , Contact.Name , "sounds\"+fileName);