Hi,
There will be a sample program for memory buffer in c:\actuate6\erdpor\examples\reusequery. That example is self explainatory for memory buffer.
MemoryDataSorter has a method called "COMPARE" with two datarow objects as parameter. By overriding this method, you can sort on two different columns in a datarow or in multiple datarows component. This compare method will return value as 0 or 1 or -1.
IF it's Zero the values are equal..
Check your manual for detailed description of memorydatasorter.
If u need any help, please feel to ask.
Cheers,
Arun.K