Dynamic dates in variants for proportion factor calculation

Hello all

As part of our demand planning we run calculation of proportional factors in a batchjob with a variant.

In the calculation transaction for proportional factors I'd like to calculate the Date from field at the top dynamically. I need it to be the first day of the current month 3 years in the past (like it's october now, so the field should contain 1st of october 2005).

However i can't seem to accomplish this with any of the dynamic date options in the variant. The closest is the (Beginning of mth-xx months, end of mth+yy months) one, but it requires two parameters and i only have one.

I can also hit the date by subtracting 761 workdays from the current date, but tha'ts not a very good solution since it will become inaccurate in the future.

Does anyone have any ideas how to accomplish this?