Are you asking about an ASP.NET page? If so then many of the controls have a postback property. Setting this to true causes the code for that control to be executed then the page will post-back to itself.
Please explain more on what you would like to accomplish, and we will be happy to help you through it.
And, if there is certain code that you have placed in the "Page_Load" procedure that you want to be able to call without reloading the page, you can create a seperate procedure and call it from the "Page_Load" procedure and wherever else you want.