This function, if called numerous time during a transaction, will slow down the process:

        ' Format a value
        ' expN1 Value
        ' expC1 Separator
        ' expN2 Number of decimals
        Public Function GetFormatValue(ByVal tnValue As Double, ByVal tcSeparator As String, _
         ByVal tnDecimal As Integer) As String
            Dim lcValue As String = ""
            Dim loCultureInfo As CultureInfo = Nothing

            ' Based on the language
            Select Case nLanguage

                ' English
                Case 1
                    loCultureInfo = New CultureInfo("en-US")

                    ' French
                Case 2
                    loCultureInfo = New CultureInfo("fr-CA")

                    ' Spanish
                Case 3
                    loCultureInfo = New CultureInfo("en-US")

                    ' Portuguese
                Case 4
                    loCultureInfo = New CultureInfo("en-US")

            End Select

            loCultureInfo.NumberFormat.NumberDecimalSeparator = "."
            loCultureInfo.NumberFormat.NumberGroupSeparator = tcSeparator
            loCultureInfo.NumberFormat.NumberDecimalDigits = tnDecimal

            lcValue = tnValue.ToString("N", loCultureInfo)

            Return lcValue
        End Function

I didn't pay attention to it until now. So far, it was mostly used on request for a few displays on a form. But, when being called thousands of times during a hit, this has a significant impact. I am moving the creation of the object at the application initialization level to have it executed only once and store loCultureInfo into oApp.oCultureInfo.