Task #1
For cells B100 and down:
Formula: copy to clipboard 
=CHAR(SUM(62,AGGREGATE(15,6,ROW(A$3:A$91)/(B$3:EZ$91<>""),ROWS(A$1:A1))))&RIGHT(TEXT(MOD(AGGREGATE(15,6,ROW(A$3:A$91)*1000+COLUMN(B$1:EZ$1)/(B$3:EZ$91<>""),ROWS(A$1:A1))/1000,1),".000"),3)-1

For cells C100 and down:
Formula: copy to clipboard 
=IFERROR(INDIRECT(TEXT(AGGREGATE(15,6,ROW(A$3:A$91)*1000+COLUMN(B$1:EZ$1)/(B$3:EZ$91<>""),ROWS(A$1:A1)),"R00C000"),)&"","")

I don't know VBA so I can't help you there. You may want to ask one of the moderators, I see Richard is a participant in this thread, how to proceed to get help from the VBA contributors.
Let us know if you have any questions.