Delay app.response window until pdf fully displayed

Hi,

I am wondering if someone can help me..

I am automating a set of actions.

My first action step is "var cRtn = app.response("Enter Invoice number");"

My problem is that this app response window appears before the pdf page has finished rendering on the screen.  I want it to fully render so that the user can read the invoice number and then input it into the window.

Is there a way to delay the window appearing until the pdf page is fully rendered and visible ?

Thanks

Andrew