Excel 2007 : Excel 2007 Trendline

Good morning,

I'm new to this forum as of today, finding it via the web. My supervisor asked me to create a chart, where he wants to show the values in a continuous line. Each line represents a specific product, the y-axis will have the amount used, and the x-axis will show the month. I'd like to be able to update this chart as new data comes in, so I'd also like to know how I could do that, too.

The MS Excel Application I have at home is 2003. I thought that the referrence guide I have for 2003 would translate over, but it doesn't. I'd be extremely grateful for the help, and thanks in advance to those that reply to this thread!