Did you check this doc for ETL/DAC?
Since you want to point W_MCAL_DAY_D instead of W_DAY_D I would suggest to extract the existing logical table into udml and replace the source table and apply back the udml to rpd.
that would be easiest way to do.
If helps mark
Edited by: Srini VEERAVALLI on Feb 11, 2013 9:11 AM
Yes, You have to use MCAL instead of DAY.
After your join in Physical layer, identify the logical table for DAY in BMM duplicate it change the source DAY to MCAL and then remap each column from DAY to MCAL.
Since you might need same logical column names re-mapping would be easiest one.
UDML might take something instead of that above said method would be easier.