Error in app_start help needed

[Jon]

I have custom error handling configured for my application. In web.config I have:

<customErrors defaultRedirect ="ErrorDisplay. aspx" mode="On">

<error statusCode="404 " redirect="Error 404.htm"/>

</customErrors>

This works very well, except in Global.asax. The following code throws an error in the data layer, which rethrows the error and gets caught in the try block below. I then throw my error (a custom class derived from the ssytem exception type). When I do this in any other page, it redirects to my custom error page as expected. However, in the App_Start of global.asax, it does not and the app goes on to display the first page of the site, not the error page. Is there a reason for this, am I doing something wrong? Thanks.

Sub Application_Sta rt(ByVal sender As Object, ByVal e As EventArgs)

' Fires when the application is started

Dim dsPriority As DataSet, oNetData As MSIData, dbCon As SqlClient.SqlCo nnection

Try

strDefConString = System.Configur ation.Configura tionSettings.Ap pSettings("Conn ectionString")

oNetData = New MSIData

dbCon = oNetData.GetCon nection(strDefC onString)

Application("Pr iorityListDS") = oNetData.SProcD ataSet(dbCon, "GetPriorityLis t")

Catch ex As Exception

Dim excNew As MSIException = New MSIException("A n error occured during application start." + ControlChars.Ne wLine + ex.Message)

excNew.TrueSour ce = "Application_St art"

Throw excNew

End Try

End Sub