It can be done as dynamic, but that in no way makes it a good idea. If you need the totals for other shuff, then

Create proceduretest1

As

begin

Declare @col1total int, @col2total int, @col3total int;

select @col1total = sum(col1), @col2total = sum(col2), @col3total = sum(col3) from Table1;

/* do other stuff with totals here*/

select @col1total, @col2total, @col3total;

end