public static int getExpressionLocByPtg( Ptg ptg, Stack expression ) throws FormulaNotFoundException
	{

		for( int i = 0; i < expression.size(); i++ )
		{
			Object o = expression.elementAt( i );
			if( o == null )
			{
				throw new FormulaNotFoundException( "Couldn't get Ptg at: " + ptg.toString() );
			}
			if( o instanceof Byte )
			{
				// do nothing
			}
			else if( o instanceof Ptg )
			{
				if( o.equals( ptg ) )
				{
					return i;
				}
			}
		}
		return -1;
	}