I am trying to get the total of 3 form fieds displayed in another form field which will update as numbers are entered. This is a php form and the all the amounts in these fields (including the total) need to be stored into the DB through the PHP on submission.

I have no idea about JS and so don't even know where to begin and I obviously can't submit the form through the JS as it needs to go through the PHP.

I hope this makes sense and that someone can point me in the right direction.