Page load before pRequest

Question

I want to call a number of javascript functions that will be enabling/disabling items based on the value of
certain items. This only happens in the case of an update. So I thought I could do this:
define a javascript function that calls all the "controls" and checks pRequest to see if it is UPDATE. If it isn't it
doesn't do anything.
function run_All_Controls() {
/* call this when page loads */
alert($v("pRequest"));
if ($v(pRequest) === 'UPDATE')
work_Pay_Control();
And I would call it in Execute when page loads:
run_All_Controls();
But this doesn't work because it seems like the page loading happens before pRequest is set.
I can see that UPDATE is passed but it follows the call to run_All_Controls();
So then when is the best place to call a javascript function that affects a lot of items in a form?

Answer 1

Well thank you Jari!
I found one way it works thanks to you, and I am stopping there because I have a whole
slew of issues to take care of in this application.
This works:
in page attributes,
function and global variable definition:
function run_All_Controls() {
alert("html header reports: " +"&REQUEST.");
if ("&REQUEST."=='UPDATE'){
work_Pay_Control();
And then in Execute when page loads:
run_All_Controls();
I did not know that one could use a construct like that to evaluate a variable from javascript. fascinating.
Definitely something to know for the future. Many thanks!