Вычислить значения функции - VB (59103)

Option Explicit
Private Enum DotAndCommaEnum
    IsNotPresent
    IsPresent
End Enum
Private Type SignType
    DotAndComma As DotAndCommaEnum
    Minus As DotAndCommaEnum
End Type
Private mlngContentOfString As SignType
Private Const A As Single = 1.3
Private Const B As Single = 1.29
Private Sub cmdCompute_Click()
    Dim dblRetval As Double, dblResult As Double, strRetval As String, lngStringLength As Long
    strRetval = txtValueX.Text
    lngStringLength = VBA.Strings.Len(txtValueX.Text)
    If lngStringLength = 1 And (txtValueX.Text Like "[-.,]") Or lngStringLength = 0 Then
        VBA.Interaction.MsgBox "Недопустимое значение X.", vbInformation, "Ошибка"
        With txtValueX
            .SetFocus
            .SelStart = 0
            .SelLength = lngStringLength
        End With
        Exit Sub
    End If
    If VBA.Strings.InStr(1, strRetval, ".") <> 0 Then strRetval = _
        VBA.Strings.Replace(strRetval, ".", ",")
    dblRetval = VBA.Conversion.CDbl(strRetval)
    Select Case dblRetval
        Case Is < 1
            dblResult = A * dblRetval + B
        Case 1
            dblResult = VBA.Math.Cos(A * dblRetval)
        Case Is > 1
            dblResult = VBA.Math.Exp(-A * dblRetval) * VBA.Math.Cos(A * dblRetval)
    End Select
    txtValueY.Text = VBA.Conversion.CStr(dblResult)
End Sub
Private Sub cmdExit_Click()
    Unload Me
End Sub
Private Sub txtValueX_Change()
    If Not txtValueX.Text Like "*[,.]*" Then mlngContentOfString.DotAndComma = IsNotPresent
End Sub
Private Sub txtValueX_KeyPress(KeyAscii As Integer)
    If KeyAscii = 45 Then
        If txtValueX.SelLength = 0 Then
            If VBA.Strings.Left$(txtValueX.Text, 1) <> "-" Then
                If txtValueX.SelStart <> 0 Then KeyAscii = 0
            Else
                KeyAscii = 0
            End If
        Else
            If txtValueX.SelStart <> 0 Then KeyAscii = 0
        End If
    ElseIf KeyAscii = 44 Or KeyAscii = 46 Then
        If txtValueX.SelStart = 0 And (VBA.Strings.InStr(1, txtValueX, "-") <> 0) And txtValueX.SelLength = 0 Then
            KeyAscii = 0
        Else
            If mlngContentOfString.DotAndComma = IsNotPresent Then
                mlngContentOfString.DotAndComma = IsPresent
            Else
                If Not txtValueX.SelText Like "*[.,]*" Then KeyAscii = 0
            End If
        End If
    Else
        If VBA.Strings.Chr$(KeyAscii) Like "[0-9]" Then
            If txtValueX.SelLength = 0 Then
                If txtValueX.SelStart = 0 And VBA.Strings.InStr(1, txtValueX.Text, "-") Then KeyAscii = 0
            Else
                If txtValueX.SelStart = 0 And VBA.Strings.InStr(1, txtValueX.SelText, "-") = 0 Then KeyAscii = 0
            End If
        Else
            If KeyAscii <> 8 Then KeyAscii = 0
        End If
    End If
End Sub