Can I set a validation for a range of cells so that the sum of the range must
always equal a certain value? For example, if I attempt to change one of the
values in cells a1:f1 I would like the user to be given a message that the
sum of the range must be equal to "1" and so they are aware that another
change in the range must be made to either increase or decrease other values
so that the sum is not affected. Thank you in advance for your assistance.