stavi na formu text box (text1), labelu (label1) i gumb (command1)
Option Explicit
Private Sub Command1_Click()
Dim i As Integer
Dim str As String
Dim br_a As Integer
Dim br_b As Integer
Dim tmp As String
Label1.Caption = ""
str = Text1.Text
For i = 1 To Len(str)
tmp = Right(str, 1)
Label1.Caption = Label1.Caption & tmp
str = Left(str, Len(str) - 1)
Select Case tmp
Case "O"
br_a = br_a + 1
Case "N"
br_b = br_b + 1
End Select
Next i
End Sub
u br_a su ti prebrojani 'O'-ovi, a u br_b 'N'-ovi (stvar je CASE sensitive, dakle ne broji 'o' i 'n') pa s njima moš šta oš
možda postoji i neki pametniji način, ali je kasno, ko bi sad išao to prčkati