Calculate Growth Percentage

I want to be able to display the percent of growth for databases on the server. My query has the file sizes and names and the dates, its done monthly . How do i create a field with the growth % from one month to the next, or from one date entry , to the next. so it appears like this

2006 2007 2008

23000 % growth 3400 %growth 20000

keep in mind, this is how it is displayed in reporting services with a matrix(crosstab)

Here's my query



Code Snippet
SELECT RC_STAT.dbo.Tbl_Database_Statistics.AutoId, RC_STAT.dbo.Tbl_Database_Statistics.Server_Description,
RC_STAT.dbo.Tbl_Database_Statistics.Database_Size_Datetime, RC_STAT.dbo.Tbl_Database_Statistics.Database_Description,
RC_STAT.dbo.Tbl_Database_Statistics.Database_Size_Mb, RC_STAT.dbo.Tbl_Database_Statistics.Database_Location,
RC_STAT.dbo.Tbl_Database_Statistics.Database_File_Name, DbSTAT.MonthlyDBTotal
FROM RC_STAT.dbo.Tbl_Database_Statistics INNER JOIN
(SELECT Database_Size_Datetime, Server_Description, Database_Description, SUM(Database_Size_Mb) AS MonthlyDBTotal
FROM RC_STAT.dbo.Tbl_Database_Statistics AS Tbl_Database_Statistics_1
GROUP BY Database_Size_Datetime, Server_Description, Database_Description) AS DbSTAT ON
DbSTAT.Server_Description = RC_STAT.dbo.Tbl_Database_Statistics.Server_Description AND
DbSTAT.Database_Description = RC_STAT.dbo.Tbl_Database_Statistics.Database_Description AND
DbSTAT.Database_Size_Datetime = RC_STAT.dbo.Tbl_Database_Statistics.Database_Size_Datetime