Allow Only positive numbers in datagridview cell

<script type="text/javascript">
   function IsNumFieldKeyPress() {
     var element;
     element = event.srcElement;
     if (event.keyCode >= 48 && event.keyCode <= 57) {//to handle num 0 -9 
         event.returnValue = true;
         return;
     }
     else if (event.keyCode == 46) { // to handle "."
        if (element.value.indexOf('.', 0) == -1) {
             event.returnValue = true;
             return;
        }
     }
     else if (event.keyCode == 43) { // to handle + 
        if (element.value == undefined)
            element.value = "+";
            else if (element.value.charAt(0) != "+" && element.value.charAt(0) != "-")
            element.value = "+" + element.value;
        }
        else if (event.keyCode == 45) { // to handle - 
           if (element.value == undefined)
               element.value = "-";
               else if (element.value.charAt(0) != "-" && element.value.charAt(0) != "+")
               element.value = "-" + element.value;
           }
           event.returnValue = false;
        }
</script>

private void dataGridView1_CellValidating(object sender,
    DataGridViewCellValidatingEventArgs e)
{
    dataGridView1.Rows[e.RowIndex].ErrorText = "";
    int newInteger;

    // Validating the 'new row', you should avoid, as your are editing it
    if (dataGridView1.Rows[e.RowIndex].IsNewRow) { return; }
    if (!int.TryParse(e.FormattedValue.ToString(),
        out newInteger) || newInteger < 0)
    {
        e.Cancel = true;
        dataGridView1.Rows[e.RowIndex].ErrorText = "Please enter only positive values";
    }
}

private void dataGridView1_CellValidating(object sender,
    DataGridViewCellValidatingEventArgs e)
{
    dataGridView1.Rows[e.RowIndex].ErrorText = "";
    int intVal;

   
    if (dataGridView1.Rows[e.RowIndex].IsNewRow) { return; }
    if (!int.TryParse(e.FormattedValue.ToString(),
        out intVal) || intVal < 0)
    {
        e.Cancel = true;
        dataGridView1.Rows[e.RowIndex].ErrorText = "the value must be a non-negative integer";
    }
}