Join that table in your query then. Select the numeric value as "LetterNumericValue" and the actual letter as "LetterValue".

Code:
select twn.number as "LetterNumericValue", twl.letter as "LetterValue"
from tablewithnumber as twn join tablewithletters as twl on twn.number = twl.number
Then you can use that in your vb.code.

vb Code:
  1. me.combobox1.DataSource = mydataSource
  2. me.combobox1.displaymember = "LetterNumericValue"
  3. me.combobox1.valuemember = "LetterValue"

Justin