It depends... as it usually does.
If each "letter" on the form is a button, then you can place a text box on the form. Make each button set the value of the text box to the appropriate letter plus the asterisk symbol (ie: A* or B*, etc), then open the query.
Kind of like this:
Private Sub cmdA_Click()
Me.Text6 = "A*"
DoCmd.OpenQuery "Query2"
End Sub
In the query's criteria line, add the criteria. Like this with appropriate modifications for your setup:
Like Forms![Form2].[Text6]
Notice there's no variable (mletter)required here.
There are lots of other ways to do this. If you have a form based on either the table or a query, you can open the form and specify the criteria in the Open command rather than in the query.
For example the code in the command button [cmdA] could be:
DoCmd.OpenForm "MyResultForm",,,"[Description] Like 'A*'"
cmdB would be the same except at the end:
DoCmd.OpenForm "MyResultForm",,,"[Description] Like 'B*'"
and so on...
The nice thing about opening a form instead of a query is that you have a lot more control over look, feel, and actions the user can take.
Hope that helps.