XML VBA Error Catching

This code gets the data from the website

http://api.yr.no/weatherapi/location...5;lon=8.555967

The information obtained from this website is then organized in a spreadsheet. I am trying to avoid crashing the program. I've noticed that if an incorrect latitude/longitude is input then the website returns an error. What would need to be added in these codes to have the code check if an error is produced and then ask the user to check their input BEFORE adding the input into the "Site List" worksheet.

Private Sub CommandButtonEditUpdate_Click()

    Dim Msg As String

    If ComboBoxEditSiteName.ListIndex < 0 Then
        MsgBox "You must select a site to edit"

    Else

        If TextBoxEditSiteName = "" Then
            Msg = Msg & "You must include a site name" & vbCrLf
        End If

        If TextBoxEditLat = "" Then
            Msg = Msg & "You must include a latitude" & vbCrLf
        ElseIf Not IsNumeric(TextBoxEditLat) Then
            Msg = Msg & "Latitude must be numeric" & vbCrLf
        End If

        If TextBoxEditLong = "" Then
            Msg = Msg & "You must include a longitude" & vbCrLf
        ElseIf Not IsNumeric(TextBoxEditLong) Then
            Msg = Msg & "Longitude must be numeric" & vbCrLf
        End If

        If Msg <> "" Then
            MsgBox Msg

        Else
            ' locate site record
            ' Write site name to cell
            ' Build URL from lat and long and write to cell

            ' clear form and leave form showing


            Dim selRow As Long
            Dim lat1 As String
            Dim lon1 As String
            Dim sitelink1 As String
            Dim sitename1 As String

            'Assign variables to construct URL
            selRow = ComboBoxEditSiteName.ListIndex + 1
            lat1 = Format(cpUserForm.TextBoxEditLat.Value, "0.0000000000000000")
            lon1 = Format(cpUserForm.TextBoxEditLong.Value, "0.0000000000000000")

            sitelink1 = "http://api.yr.no/weatherapi/locationforecastlts/1.2/?lat=" & lat1 & ";lon=" & lon1
            sitename1 = cpUserForm.TextBoxEditSiteName.Value

            'Write values to spreadsheet cells.
            Worksheets("Site List").Cells(selRow, 1) = sitelink1
            Worksheets("Site List").Cells(selRow, 2) = sitename1
            Worksheets("Site List").Cells(selRow, 3) = lat1
            Worksheets("Site List").Cells(selRow, 4) = lon1


            AddClear
            LoadComboBoxEditSiteName
            LoadListBoxDeletePickSiteList
            EditClear
        End If
    End If
End Sub

Private Sub CommandButtonAddUpdate_Click()


    Dim Msg As String

    If TextBoxAddSiteName = "" Then
        Msg = Msg & "You must include a site name" & vbCrLf
    End If

    If TextBoxAddLat = "" Then
        Msg = Msg & "You must include a latitude" & vbCrLf
    ElseIf Not IsNumeric(TextBoxAddLat) Then
        Msg = Msg & "Latitude must be numeric" & vbCrLf
    End If

    If TextBoxAddLong = "" Then
        Msg = Msg & "You must include a longitude" & vbCrLf
    ElseIf Not IsNumeric(TextBoxAddLong) Then
        Msg = Msg & "Longitude must be numeric" & vbCrLf
    End If

    If Msg <> "" Then
        MsgBox Msg
    Else
        ' Create a new site record
        ' Write site name to cell
        ' Build URL from lat and long and write to cell

        ' clear form and leave form showing

        Dim emptyRow As Long
        Dim lat As String
        Dim lon As String
        Dim siteLink As String
        Dim siteName As String

        'Assign variables to construct URL
        emptyRow = Sheets("Site List").Cells(Rows.Count, 2).End(xlUp).Offset(1).Row
        lat = Format(cpUserForm.TextBoxAddLat.Value, "0.0000000000000000")
        lon = Format(cpUserForm.TextBoxAddLong.Value, "0.0000000000000000")
        siteLink = "http://api.yr.no/weatherapi/locationforecastlts/1.2/?lat=" & lat & ";lon=" & lon
        siteName = cpUserForm.TextBoxAddSiteName.Value

        'Add values to site list worksheet
        Worksheets("Site List").Cells(emptyRow, 1) = siteLink
        Worksheets("Site List").Cells(emptyRow, 2) = siteName
        Worksheets("Site List").Cells(emptyRow, 3) = lat
        Worksheets("Site List").Cells(emptyRow, 4) = lon

        'Refresh lists
        AddClear
        LoadComboBoxEditSiteName
        LoadListBoxDeletePickSiteList

    End If

End Sub