Only 1 P in textbox

Hi everybody,

I want to have only 1 P in textbox.

I already have this:

[code]
 Public Function ValidateBankNumber(ByRef strValue As String) As Boolean
        Dim blnResult As Boolean
        Dim strCheckValue As String
        Dim character As String
        Dim digitsOnly As Boolean
        'Dim ascii As Integer = Convert.ToInt16(By.KeyChar)

        strCheckValue = strValue

        blnResult = False
        digitsOnly = True
        Dim i As Integer
        Dim intValue As Short
        Dim intCount As Short

        If UCase(Left(strCheckValue, 1)) = "P" Then 'Giro
            strCheckValue = CStr(Val(Right(strCheckValue, Len(strCheckValue) - 1)))
            If Len(strCheckValue) <= 7 Or ((UCase(Left(strCheckValue, 1)) = "P") = True) Then
                For i = 1 To Len(strCheckValue)

                    character = Mid(strCheckValue, i, 1)
                    If character < "0" Or character > "9" Then
                        digitsOnly = False
                        Exit For
                    End If
                Next i
                blnResult = digitsOnly
            Else
                blnResult = False
            End If
        Else 'Bank
            If Len(strCheckValue) = 9 Then
                For i = 1 To 9
                    character = Mid(strCheckValue, i, 1)
                    If character < "0" Or character > "9" Then
                        digitsOnly = False
                        Exit For
                    End If
                    intValue = CShort(Val(character))
                    intCount = CShort(intCount + (intValue * (10 - i)))
                Next i
                If digitsOnly And (intCount Mod 11) = 0 Then
                    blnResult = True
                Else
                    blnResult = False
                End If
            Else
                blnResult = False
            End If
        End If
        ValidateBankNumber = blnResult
    End Function
[/code]

But now it is allowed to have more then 1 p in a textbox But How to make it that it is only allowed to have 1 p?

THX