How do I update 'zoom' status in my PDF viewer?

Q:

I need to know if there are any method similar to SetCurrentPageProc
(Example: _pdfview.SetCurrentPageProc(AddressOf UpdateStatusBar,
main_form))

Because I need to show the zoom in the status bar. I want to do
something similar that you do in the example 'PDFView' to show the
number of page.
------
A:

There is no direct callback function to notify your application when
the zoom ratio is changed. Nevertheless since your application is
explicitly calling pdfview.SetZoom(...) you can invoke a custom
callback or update widget variable at the same point (e.g. just after
invoking SetZoom()).