Yes, 0 to 9 gives 10 extra characters so 36^3 = 46656

A1 =ROW()-1 and fill down to A46656
B1 =MOD(A1,36)+IF(MOD(A1,36)<26,65,22)
C1 =INT(MOD(A1/36,36))+IF(INT(MOD(A1/36,36))<26,65,22)
D1 =INT(MOD(A1/36/36,36))+IF(INT(MOD(A1/36/36,36))<26,65,22)
E1 =CHAR(B1)&CHAR(C1)&CHAR(D1)


If case sensitive then you could also include lower case alpha which would then give you 238328 unique codes. I'll let you have a try at that one.