How to calculate percent change for months

Calculate % change between months with relational data

Steps:--Add Order year, Month, count(Order number) in List
-- Under the query:
--create "data item1" with expression moving-total([count],2)
--create "data item2" with expression ([Data Item1] -[count])
--create "data item3" with expression ([count]- [Data Item2])
--create "% change" with expression (if ( (([Data Item3] * 1.00)/([Data Item2] * 1.00)) is null) then (1) else ((([Data Item3] * 1.00)/([Data Item2] * 1.00)) ) and add it to the List as 4th column