How to use VB code in SharePoint Designer

Hi,
I am new in SharePoint Designer.
I like to create a web page with some VB code functions (I want to convert one web site that created by Visual Studio 2005 to SharePoint server with SharePoint Designer tool).
But I always get the error when I tried to copy the VB function from Viscao Sdeio 2005 to SharePoint Designer's page.
Can you help me on this or send some example to me?
 
Thanks,
Xiao Qi
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