IF ... ELSE ... ENDIF construction.
You can make conditional calculations for one or several
rows. Click 
button to insert IF ... ELSE construction into your calculation. Type a
logical expression in "Expression" cell of the row with "IF" in "Variable" cell. When this logical expression
is TRUE, then the group of rows between "IF" and "ELSE" lines will be
used in calculation. Else, the group of rows between "ELSE" and
"ENDIF" will be used.
