I know CRJ does not have an auto throttle.
I know one has to manage cruise speed yourself.
But..... I also know a CRJ does not have a pause at TOD, even more a CRJ does not have a P button.
So if you need to leave your cockpit for a short time, or you need to figure out your approach because the wind changed here is a solution.
Download and install the freeware FSXPILOT software.
In cruise at autopilot start FSXPILOT enter your speed in FSXPILOT and press AP in FSXPILOT.
The CRJ autopilot manages navigation while the FSXPILOT takes care of constant cruise speed.
Do whatever you need to do and when you return in the cockpit disable AP in FSXPILOT and continue your normal procedures.
FSXPILOT can be downloaded here
And yes I know .........