Well, it is normal for it to rise some during exercise, that is why the docs tell you to do it. If it races, then that is a different story, but to just supress, that would not be a good idea, it is healthy for it to elevate during exercise.
Beta blockers supress the heart rate. I know this from experience. My training level has dropped from the 120 bpm range to about 90 at the same exercise level. I am on Sotalol for Afib. However, as SassyLassie says, unless you are suffering from tachycardia, there is no problem with increased heart rate during exercise; that is what is supposed to happen and you wouldn't want to medicate to prevent it.
What is behind your question?