No question here just a procedure for the archive.

Return a random letter for each cell in selection

Sub RandomLetterGenerator()

'Returns a random letter in each cell in selection
On Error Resume Next
Selection.FormulaR1C1 = "=CHAR(TRUNC(RAND()*26+65))"

'Paste value the formulas

Selection.Copy

Selection.PasteSpecial Paste:=xlValues, Operation:=xlNone, _
SkipBlanks:=False, Transpose:=False
Application.CutCopyMode = False

End Sub

search criteria
return random letters
insert random letters
generate random letters