Separate YTD pension records for employees for each company pension scheme

One of our clients has recently switched pension providers from SMART to NEST. I need to move all of the employees over from the SMART pension scheme to the NEST pension scheme but keep their respective year-to-date separate between each scheme.

At the moment, when you remove an employee from one company scheme and enroll them into the new scheme, it automatically transfers their year-to-date pension contributions to the new scheme as if they had been a member all year and completely removes any record of them being enrolled in the old scheme.