Script Component Task: Function That Returns Last Word In A String

I have a field called CustomerName Varchar 100 and I wish to write a function that can do the following in a script component task

create a function called CleanString (ByVal CustomerName as String) As String

CleanString Returns  the last word of a Customer name if the CustomerName field contains more than one word or if the CustomerName field does not contain Corp or Ltd

ie parse 'Mr John Tools'  and the function returns 'Tools'

ie parse 'TechnicalBooks' and the function returns 'TechnicalBooks'

ie parse 'Microsoft Corp' return 'Microsoft Corp'

ie parse 'Digidesign Ltd' return 'Digidesign Ltd'

Any idea of a regular expression or existing piece of existing code I can have

thanks in advance

dave