/// <summary>
        /// Reset the form values
        /// </summary>
        public void ResetForm()
        {
            selectedParentVariable = null;
            selectedParentTreeNode = null;

            foreach (Control field in this.Controls)
            {
                if (field is TextBox)
                {
                    ((TextBox)field).Clear();
                }
                else if (field is ComboBox)
                {
                    ((ComboBox)field).SelectedIndex = 0;

                }
            }

        }
        /// <summary>
        /// Populate form with values from an existing tree node
        /// </summary>
        /// <param name="node"></param>
        private void populateForm(StatTreeNode node)
        {
            if (node == null)
            {
                return;
            }

            // Disable editing if node selected parent level is greater than 3
            if (node.Level > 3)
            {
                formPanel.Enabled = false;
                return;
            }
            else
            {
                formPanel.Enabled = true;
            }

            // Get variable from selected node
            Variable sv = (Variable)node.Tag;

            // Set selected parent nodes
            selectedParentTreeNode = node;
            selectedParentVariable = sv;

            // Set level of NEW node
            tbVarLevel.Text = (node.Level + 2).ToString();

            // Get the name of the selected node
            tbParentVariable.Text = sv.getNameAtLevel(node.Level + 1);
            
            // Populate text and comboboxes
            cbKretstyper.SelectedValue = sv.fk_kretstyper;
            cbTimeUnit.SelectedValue = sv.time_unit;
            cbUnit.SelectedValue = sv.unit;
            chkbShowUnit.Checked = sv.showunit;

        }