Vb windows form: null value in datagrid

[a Wellner]

I am creating working in VB 2005 express edition on a windows form application, I am very new to VB, but do have some experience with Access and Access VBA
I am having some trouble with this code

Private Sub VehDataGridView_CellValidating(ByVal sender As Object, ByVal e As System.Windows.Forms.DataGridViewCellValidatingEventArgs) Handles VehDataGridView.CellValidating
        Dim row As Int16 = 0
        Dim numrows As Int16 = Me.VehDataGridView.Rows.Count
        Dim angle As Int16
 
 
        While row + 1 < numrows
 
            Dim rownum As Int16 = 1 + row
            angle = Me.VehDataGridView.Item(2, row).Value
            checkangle(angle, rownum, row)
 
 
            row += 1
        End While
 
    End Sub
    Sub checkangle(ByVal angle As Int16, ByVal rownum As Int16, ByVal row As Int16)
        If angle > 360 Or angle < 0 Then
            Dim message As String = " Pleese enter a angle between 0 and 360 in row " & rownum
            MessageBox.Show(message, "input error", MessageBoxButtons.OK)
            Me.VehDataGridView.Item(2, row).Value = 0
 
        End If
    End Sub

When a new row is created in the datagrid it returns an exception

System.InvalidCastException was unhandled
Message="Conversion from type 'DBNull' to type 'Short' is not valid."


On the line
“angle = Me.VehDataGridView.Item(2, row).Value”

I can’t figure out how to handel this excepton.
What I want is, if the value is null the sub checkangle not be called

So far I cant seem to be able determine when the value of Me.VehDataGridView.Item(2, row) is null.

My guess is the answer is obvious but I cant seem to figure it out.

Thank you for your help