openxlsx: append data to an existing sheet

Hello,
I'm looking for a way to modify an existing sheet from a workbook using openxlsx.
I've been reading the web, but I can't find and example doing this task.
Java isn't working in my PC.
Thanks for your time and interest.

The writeData() function of openxlsx has the arguments startCol and startRow that allows you to append data. To use that, you have to know how many rows and columns are already used on the sheet. Do you have that information?

If you provide more details about what you need to do, someone might be able to give more specific advice.