How to set item values when redirecting to the same page.

Question

I just created a redirect button that I want to redirect to the same page and set the 2 page items on the page to the same value they had before the redirect.
But I can't write:
Set These Items: P1_Permit_Number,P1_Fishing_Year
With These Values: &P1_Permit_Number.,&P1_Fishing_Year.
Because there are no values in the session state, since a submit has not been done.
So how do I do this?
I know how to get the values stored in the items, e.g., $v('P1_PERMIT_NUMBER')
but where do I place that command? It's not allowed under "With These Values"
And I don't really want to make this a submit button and create a process that says:
P1_PERMIT_NUMBER := $v('P1_PERMIT_NUMBER') because that would complicate the page too much -- I already have other processes and branches on the pages whose conditions would have to be modified so that they don't run during this scenario.
Thanks.

Answer 1

Thanks Gary and Andy. I rewrote the function according to above instructions:
function redirectToURL()
var permitNumber = document.getElementById('P1_Permit_Number');
var fishingYear = document.getElementById('P1_Fishing_Year');
var url = 'f?p=&APP_ID.:1:&APP_SESSION.::::P1_Permit_Number,P1_Fishing_Year:' + permitNumber +',' + fishingYear;
window.location.href = url;
But when I entered a value for permit number and fishing year and redirected, the word "null" appeared in the Permit page item, instead of the permit number that I had entered.
Remember that I am not submitting here. So if the syntax you showed me, i.e. getElementById('P1_Permit_Number'), searches for the item's session state, then it will be wrong, since there is no session state value for the items at this point. Perhaps that is the reason I got the null?
If so, what can I do?