Bounding a paragraph to a shape

I am working on creating a AE template that will pull information from an Excel spreadsheet and place that information in various locations within the comp. One of the cells in Excel will be a comments section and this section can get lengthy at times. So, what I am trying to do is setup a text box that is W:1300pix by H:720pix, and when the texts reaches W:1300pix it will break and start a new line below it and when it reaches the max height of 720pix it will auto scale down so that the paragraph will fit inside the box. 

The text box works great with adding the line breaks but as soon as the texts go past the max height it gets cut off. Is there an expression that I can add to the text box or source text that when the paragraph reaches it max height it will auto scale down?