Generate Unique 15 character string

I'm looking to set a property value to a unique 15 character string. This number is used as an identifier, not a security related key.

In my database this value is entered by default using substring(replace(CONVERT(varchar,newid()),'-',''),(15),(15)).

I would like to be able to reset this number to something new with a button click. Is there anyway to do this programmatically through an event handler property value rather than a database trigger?

Thanks.

If I understand this correct you are searching for something like:
Guid.NewGuid().ToString("N").ToUpper()

This is perfect, Thanks!