Just turn that same query into an INSERT ... SELECT... statement and save the data into a table along with the date and time that you collected the information. Then you can generate a report. There's no way just from the DMO you're querying to see what's happening over the week. You have to store that information in some manner.
"The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood"
- Theodore Roosevelt
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SQL Server Execution Plans
SQL Server Query Performance Tuning