/// <summary>
		/// Adds an expression to the expressions list.
		/// </summary>
		/// <returns>
		/// A <see cref="SyntacticalExpressionWidget"/>
		/// </returns>
		private SyntacticalExpressionWidget AddExpression()
		{
			
			SyntacticalExpressionWidget widget = 
				new SyntacticalExpressionWidget(this);
			
			synEdExpressionsVB.Add(widget);
			
			foreach (SyntacticalExpressionWidget expWidget in synEdExpressionsVB) 
			{
				expWidget.CheckPosition();
			}
			
			
			synEdExpressionScroller.Vadjustment.Value = synEdExpressionScroller.Vadjustment.Upper;
			
			return widget;
			
		}
		/// <summary>
		/// Removes a expression from the expression list.
		/// </summary>
		/// <param name="widget">
		/// A <see cref="SyntacticalExpressionWidget"/>
		/// </param>
		public void RemoveExpression(SyntacticalExpressionWidget widget)
		{
			synEdExpressionsVB.Remove(widget);
			
			foreach (SyntacticalExpressionWidget childWidget in 
			         synEdExpressionsVB.Children) 
			{
				childWidget.CheckPosition();
			}
		}