Producing Baseline S-Curves even after some activities were started/finished

Hello my dear fellow planners.

I would like to ask some assistance, I am having a hard time plotting the late and early curves of my schedule (Primavera  v6.2).

The situation is that, during FEED phase, EPC Schedule was drafted and some of the activities on FEED Phase were used as

predecessors for EPC so now that I am setting up the S-Curves for progress monitoring, I am having difficulty because I want to set

the Zero-Point / Start-Off point of EPC Progress Monitoring specifically from the activities which were started but at least not finished.

Is this possible?, setting the zero point on the middle of the ongoing activity?

 

Thanks, merry christmas and happy new year.