Could someone help me with the following problem in excel:

I would like to be able to generate 20 random numbers whereby the
number generated is between say -15 and 40 where once all the numbers
are generated the average of all 20 numbers is 8 for example. I guess I
could generate 19 random numbers with the above parameters and the 20th
number would be a plug to achieve the correct average but was wondering
if there was another way.

Thank you for your help.


Answer can be either through using excel itself or through a macro code
for excel.