@helpmeplease if you want the structure of your Excel file unchanged and just change values there are these options, if you must change data on a pre-formatted sheet (otherwise you might just replace this sheet). The Excel Cell Updater can change values in specific cells.
You can use a community node to write to an Excel file without changing the structure or formats:
You can the use Python and OpenPyxl to do more complex editings of excel files. You will have to plan ahead what this does to you files.
Otherwise you might indeed use the Continental Nodes to format your excel sheet after you have exported the data (this might be the safest option from a KNIME persspective).