How to conditionally display a Yes/No message box...

Question

Hi guys,

I need to display a message box conditionally, I hope you can help me. The situation is this, I have a data entry application and on my Save button, it checks first if the record exists in the database. If it doesn't, it creates a new record. And if does, I would need to display a Yes/No dialog box asking the using if the record is to be updated or not. I should be able to capture the users selection so that I can perform the update or not. This basically left me not consider adding an attribute to my button and I cant use ajax toolkit or jquery. Please help me guys... Thanks...