Returns the member that is a specified number of positions following a specified member along the member's level.
Member positions within a level are determined by the attribute hierarchy's natural order. The numbering of the positions is zero-based.
If the specified lead is zero (0), the Lead function returns the specified member.
If the specified lead is negative, the Lead function returns a prior member.
The Lead function is similar to the Lag function, except that the Lag function looks in the opposite direction to the Lead function. That is, Lead(n) is equivalent to Lag(-n).