Hi,
Not sure what format you want, but if the part number is in E10,
This formula in a cell will return the digits that follow CH:
=IF(ISNUMBER(MID(E10,3,2)*1),MID(E10,3,2),MID(E10, 3,1))
and this next formula in another cell will return the digits that follow R
=IF(ISNUMBER(RIGHT(E10,2)*1),RIGHT(E10,2),RIGHT(E1 0,1))

Hope this is helpful
Regards - Dave.