Spreadsheet formulas can do more than math calculations; they can also extract data from an API such as Facebook's. Since you may want to track more than one page -- not only yours but competitors' -- we'll set it up to be easily scalable.
In the first column, list the Facebook accounts you want to track. In the second column, create a formula to find number of likes from the API using this format:
https://graph.facebook.com/accountID (replace that with the account ID or name)
To do so, your column B formula needs to add the URL root "https://graph.facebook.com/" to the account name from column A, like so:
and so on for the other rows.