Sandy Mann wrote...
To convert the assessment in, say cell F20, to the appropriate number try:

=3*(CODE(F20)-48)-(2-(CODE(UPPER(RIGHT(F20)))-65))

ie 5c will be converted to 15
....

Alternatively,

=3*LEFT(F20,1)-SEARCH(MID(F20,2,1),"cba")+1

which has the added advantage of catching invalid entries. If F20
contained "9x", this formula would return #VALUE! rather than 48.