Marcus,
To clarify, assume I set the sample rate at build time with the samp_rate variable within the QT GUI Frequency Sink. At run time, the bandwidth (x axis) is reflective of this samp_rate. However, if I have a source block upstream that changes the sample rate via out of band means, I would like that source block to change the samp_rate of the QT GUI Frequency Sink programmatically. I am able to change the frequency of the QT GUI Frequency Sink programmatically through the message port, but I haven't seen a way to change the samp_rate/bandwidth.
Jason