Yes, there is a way to autofill a city and state from a zipcode in Excel. Here are the steps:

1. Open a new Excel worksheet and enter the zip codes in one column.
2. In the adjacent column, enter the following formula:
   Formula:

   =VLOOKUP(A2,'Zip Codes'!A:B,2,FALSE) 

   Note: Replace "A2" with the cell reference of the first zip code in your list. Also, make sure to create a separate worksheet named "Zip Codes" with two columns: one for zip codes and one for city and state.
3. Press Enter to apply the formula to the first cell.
4. Drag the formula down to autofill the remaining cells in the column.
5. The city and state corresponding to each zip code will be automatically filled in.

That's it! Now you can easily autofill the city and state for all 400 addresses by simply entering the zip codes.