Conditional splashscreen in Excel 2000 Macro

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I have created a userform as a splashscreen in a workbook which contains a saveas control to prompt the user to save the masterfile with a specified filename to a location of the users choice. This auto starts when the workbook is opened, however this splashscreen is then also live in the then saved as workbook. How do I specify the splashscreen to only run if the workbook is the masterfile.

Appreciation for any help offered. thanks