Is there a way to create a custom format for text data? Basically, I
am looking for the format to be a description lookup, while the cell
itself has the value of the item being looked up. I realize I could do
this with a separate column and use the VLOOKUP() on a table of the
values and the descriptions. However, I am just wondering if it is
possible to do the same thing with a custom format, within the cell
itself.

As an example, the following list might be some examples of values and
the descriptions I would like to see displayed:

a = Alpha
b = Beta
b1 = Beta One
83 = Category 83

So, if I enter "a" in a cell, that would be the value of the cell, but
"Alpha" would be what is displayed for the cell. Similar to what can
be done with months (i.e. 1=Jan, 2=Feb, ..., 12-Dec), but on text data.