Check for changes on update form

[admin]

I have an update form that works great but want something to check if any data changes were made to the form after hitting submit. Currently when I hit submit button I get my message "Data updated" but want something to check if no changes were made to the form and then give me message "No data changes made to update form". I read about "onchange" event but it doesnt seem to check if any data changes were made to the form.