Not sure if this is what you're looking for, but if you just want to know how to simulate a colspan...

In Excel... select the cells you want to turn into one, right click, select "Format Cells..." Click on "Alignment" tab, check the box "Merge Cells".

In Word... select the cells you want, right click select "Merge Cells".

If you already knew this and your problem is more complex, then please disregard.