Excel issues

I hav used Excel application scope. Basically I am trying to paste some images in the excel one below the other in a single sheet.
The first iteration involves pasting an image into the excel and I am saving it and it closes later. thats fine.
But the second iteration involves opening the same excel and pasting another image below the first image ( which is not working for me). Issues here are -

  1. its opening a file (not sure if its the same file I had used in first iteration ) with the same name but it has no image which I had pasted in the first iteration.
  2. to paste 2 images one below the other, I tried page down and click on an empty cell. I know this is not a standard as I will not know how many cells in exact would the first image occupy.

So is there any work around for these 2 problems?
any help is appreciated