It can be done:

=MID("1a1b1c1d2a2b2c2d",SUM((A2:C2A3:C3)*{8\4\2}) +1,2)

Ola Sandstrom

Hold down Ctrl and Shift, then hit Enter to confirm the formula.
A2:C2 is your reference numbers
A3:C3 is your values