Adding a stylesheet to a css widget

This is my first post so apologies if I put this in the wrong place.

I want to know how easy it is to add my own stylesheet to a widget and can I upload the new stylesheet to my website if the main code is on another website?

The widget is here: http://site_01504_012.ticketsoftware.net/TNWidgetMaker2.aspx

Any help would be appreciated.

Del

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