For an exercise on how to query database size and growth this is a fun project, but I would agree with other posts that this solution may not be enterprise ready yet.
I would take the table you are using for tracking growth out of MSDB and put it in a User database instead. It's not best practice to use system db for custom user applications and you may find the table vanishes if you apply a service pack or hotfix at some point. It probably wouldn't, but better safe than sorry.
The create DDL has an error in it - as someone else pointed out. The table created is called DBInformation and the ALTER statement is looking for DBInfo. I'm guessing you have both of those tables in MSDB and that's why you didn't get an error when testing the script before posting it here. You may want to drop that table in MSDB so you don't get confused later.
Connecting Excel to multiple servers to get the information is not ideal - especially if you want to give the spreadsheet to others for review. There could be security issues involved that would require troubleshooting down the road. You may want to consider consolidating the information from many servers into 1 db on 1 reporting server. SSIS will make this very easy for you using variables, configurations, and expressions.
You may also want to fire up SSRS for reporting as well to make things easier. That way you can review the results any time you wish or have it emailed to you at the an interval that is appropriate.
Like I said, this is a good beginning to your monitoring project - and a great way to get familiar with some inner workings of SQL Server. Long term however, you will more than likely want a third party application to do this for you. The last thing you want is to be the person that has to maintain the custom solution and troubleshoot issues when they arise. Especially since you are using undocumented stored procedures in your code - this solution could break with any service pack or upgrade. Same goes for sp_MSForEachTable - it's undocumented and may be removed in newer releases.
Good job! Happy hunting.