Any approach can reconfigure parameters for top_block while it's running

Dear all,

I’m wondering is there any approach can reconfigure the parameters for
top_block while it is running. I’ve seen a video on Youtube that
implemented the tuning frequency hopping, which is named “A program
written for the GNU Radio that changes the TX frequency of the USRP”.
This video shows the parameters of the top_block are reconfigurable
while it is running, and I really desire to know how to reconfigure
these parameters passed through the main() to top_block while the
top_block has already start working. Your help will be fairly high
weighed for me, since this is the last step of my project. Really