1.How to make arguments optional in a function?

A.Suppose there is alogin window in the user name we can type Any thing but while running its giving som eerror we can avoid tht error actually so, we can make tht tsl as an optional so tht if an error occurs it countinues but not stop for exampleOptional.Dialog("Login").WinEdit("Name:").Set "ssss" these line make an optional now