Editing Cells From Access

I have some VBA code in an Access DB that opens an Excel spreadsheet at a specific workbook, and then performs some formatting on the sheet, before saving the changes and closing the workbook.

The first time i run the sub it works perfectly. If i then try and run it again i get a run-time error 91 message (Object variable or With Block variable not set). This happens every subsequent time i try and run the code until i manually reset.

The error message is always at the same point. Here's the

I've put ***ERROR MESSAGE HERE*** at the point in the code the error seems to be occuring