After 2 days searching I give up. I have a form and need to add (autofill) taxes to the input total price but in a easy simple way:
<form name="form" action="go.php"> <input name="cost" type="text"> <input name="costplustax" type="text" value=" here we autofill cost +19%> <input type="submit" value="ready to mysql">
cost 100.000 because tax is 19% then we autofilll the input with onblur or onMouseOver to 119.000
How to do this?