How do I export a table from Access into an already existing Excel workbook on a specific tab, without erasing what it written on the other tabs?

i don't think you can

the transferspreadsheet command and the file export both produce new spreadsheets

might not help
but how about export the table/qry outwith a date stamp this would input this into a new spreadsheet so if your after the tab in he spreadsheet to be call George then have abutton commant to do george ddmmyyy possible hrs and mins as well

not look to much into transfer spreadsheet yet but it must be-able to put a stamp on it failing that how about next number - plenty of number codes generators out their ???
As i said might not be of much help - but it would get round your problem

I'm not familiar with Excel macros, but if it can be done, try creating a macro that takes a worksheet and copies it to a specific location. Then, whey you export from Access, you will blow away the existing worksheet, create a new one and then have the Excel macro move the data somewhere else.