Think that you may work with synthetic dimensions, please check OL-Help for VALUELIST (or VALUELOOP). Likewise you may create an island-table with the dimensions required.
In any case, you need to create for each dimension then a separate expression, referring then to the position of the Valuelist with a couple of IFs:
IF(VALUELIST('A', 'B', 'C') = 'A', ......
It is somewhat easier to have an island-table (you may add additional comments related to the dimension and convert to numeric values with DUAL), then expression may look like
Though the question might be allowed, why to include several measurements into one chart and scale, but this might be decided by the dataowner.