How delete a value of a field with button

If the filed is a Text Field, you can you just delete it manually, otherwise please provide more info as to why you believe a custom button is needed.

Its a date field and i need to delete the date... and update it to blanc
so i have to go day--- month and year searching from blanc value

its easier and faster i need to delete the field date, clic, and the save the record....

Got it
add this code in Client before

var ctrl = Runner.getControl(pageid, 'NAME FIELD');
ctrl.clear();

You can try:

1.) Create a custom button.
2.) In the Client Before tab enter:
var ctrl = Runner.getControl(pageid, 'Fecha');
ctrl.clear();
3.) Be sure to clear out any default entries in the Server tab and Client After tab.

Hope this works for you.

Paul