Modal Pop-Up

Question

Hi I have an ASP.NET page. During exection , If a particular condition is satisfied I need to pop-up a modal window and ask for some inputs which i need in the calling page and continue with the rest of the calling page . If the condition is not satisfied the page should continue execution without the pop-up. My doubt is how do i trigger a pop-up dynamically with out any specific click event happening Thanks TechTalker