There are two systems for finding dates of death. If the person died after 1855 in Scotland it will be recorded in the GRO which you can access on line at www.origins.net
There is a small charge for using this system but worthwhile. However, you do need to know roughly when the person died, where they lived, etc.
In Scotland you are allowed to look at the certificate without purchasing it but this obviously means you need a researcher in the GRO to do this looking. This can be very expensive.
Pre 1855 is much more difficult. The fortunate few have a gravestone and many of these have been recorded. Which county of Scotland do your ancestors come from? If it is Sutherland then please put some more info up or email me and I will try to help.
Christine