Displays a message box with indicated icon and buttons.
Buttons: Value from .NET messageboxbuttons enumeration in string form
Valid Values: ("OK", "OKCancel", "YesNoCancel", "YesNo"),
Icon: Value from .NET messageboxicon enumeration in string form
Valid Values: ("None", "Error", "Hand", "Stop", "Question", "Exclamation", "Warning", "Information", "Asterisk"),
Callback: returns a "result" number indicating the value of the button clicked
Valid Results: ("None" = 0, "OK" = 1, "Cancel" = 2, "Yes" = 6, "No" = 7).