Hola. modificando y agregando un poco de codigo al algoritmo de karen81 te hice esto...
Codigo:
Private Sub Form_Load()
Dim DatoAscii
Dim DatoBinario As String
DatoAscii = "A" "ingresa aca el caracter ASCII a pasar a binario
DatoBinario = Hex2Bin(Left(Hex(Asc(DatoAscii)), 1)) & Hex2Bin(Right(Hex(Asc(DatoAscii)), 1))
MsgBox DatoBinario "ascii en binario
End Sub
Private Function Hex2Bin(DatoHex As String) As String
Select Case LCase(DatoHex)
Case "0"
Hex2Bin = "0000"
Case "1"
Hex2Bin = "0001"
Case "2"
Hex2Bin = "0010"
Case "3"
Hex2Bin = "0011"
Case "4"
Hex2Bin = "0100"
Case "5"
Hex2Bin = "0101"
Case "6"
Hex2Bin = "0110"
Case "7"
Hex2Bin = "0111"
Case "8"
Hex2Bin = "1000"
Case "9"
Hex2Bin = "1001"
Case "a"
Hex2Bin = "1010"
Case "b"
Hex2Bin = "1011"
Case "c"
Hex2Bin = "1100"
Case "d"
Hex2Bin = "1101"
Case "e"
Hex2Bin = "1110"
Case "f"
Hex2Bin = "1111"
Case Else
MsgBox "Valor no admitido!"
End Select
End Function
Espero que sea lo que necesitas. Saludos.