Sure there is, in fact 2 ways you can do this... this first is using PHP... what you do is when the user clicks submit.. you make the html action tag to to another script that authenticates, ie checks, to make sure all the fields have the values needed.
Another BETTER way is simply to use javascript... all you do is in the html tag write the following....
<yadda yadda yadda onclick="ValidateFields()" yadda >
Then have a function declared somewhere that checks to make sure all of your vields are NOT NULL... and then your done
rgds,
Swixy