Report builder, show only different archive values

Report builder, show only different archive values

Hello all,

We use MS report builder to generate report. We have tablix control to show values from archive.
Now we have row group by timestamp, and archive values for motor speeds every N seconds. 
How to show only values which are different then previous one?
Example for current situation
Time             M1      M2       Unit
12:08:00      200     123       rpm 
12:08:30      200     123       rpm
12:09:00      223     123       rpm

In the first two rows, no change of values, so how to select only first row and show it?!

Final result shoud be:
Time             M1      M2       Unit
12:08:00      200     123       rpm 
12:09:00      223     123       rpm

BR, MK