>Did you try the operation without SUM the variable?
No, I have not try that. But I am not sure I understand what do you mean by "without SUM the variables"? Removing the variables?
"The creative process is nothing but a series of crises." Isaac Bashevis Singer
"My experience is that as soon as people are old enough to know better, they don't know anything at all." Oscar Wilde
"If a nation values anything more than freedom, it will lose its freedom; and the irony of it is that if it is comfort or money that it values more, it will lose that too." W.Somerset Maugham
