eDNA Expert @Greg has created a phenomenal DAX pattern section that directly addresses both of your questions::
Re: doing this as a measure – @Greg works through the preferred way to do this, using variables to capture the current row context, rather than EARLIER.
Re: getting it to work after filtering on Company - he works through this as well, in terms of how to apply the pattern with ALLSELECTED, rather than ALL.
If you still have any questions after working through his material, please just give a shout.
- Brian
P.S. Your username kills me every time I see it… 