Looks like this is where it's being set:
Code:
var filename = document.formlogin.trackingnr.value.toUpperCase() + ".html";
My guess on a change would be something like this...
Code:
var filename = "transactions/" + document.formlogin.trackingnr.value.toUpperCase() + ".html";
Might not work, especially witohut having a chance to see exactly what the trackingnr.value is, but eh... with a bit of tweaking (if needed), I'm sure you'll make it do what it should.