JQuery Alerts

I have a website where people select a date from a date picker and then they select a Start Time and an End Time for the Event. I need some JQuery Alerts to pop up if the data is not what it should be. One Alert needs to check the Date in the Date Field and if it is earlier than the current date I need them to see an Alert that says they can not select a date prior to today. Another one would be if they select the Start Time (it is a drop down) and then an End Time, I want to prevent an End Time earlier than the selected Start Time. Another would be if they select Yes on a different field (Yes/No Radio button) then the Date field is required. I can provide all the necessary field names and what I would like the Alerts to say when they pop up but it would be difficult to provide access to the actual files. I could provide access to a temporary set of files I believe but only for viewing on the web not for editing. I would need the Alerts sent to me in Text format and I would add them to my file and then test for accuracy.