That is something you would have to ask your doctor about, but I'm pretty sure that samples are not available in meds that are controlled substances, which Valium is. More likely, you would have to get your doc to prescribe a small amount to try.
If you think you need valium you need to go to your doctor and tell him/her just that. This is serious stuff though. They are highly addictive ! You need a doctor to regulate your usage. Please do not get valium from your friends etc. because you are only asking for trouble. We do not care about addiction until we have to quit and then we wish we had never started.