It should be fairly easy with a visual basic macro in excel.

You could create a macro that does the following:
1. Type coordinates in cells or if cells already contain coordinates copy them to clipboard. (copy function)
2. focuse window on GE when it is open.
2.1 If it is not open, you have the macro open GE.
2.1.1 Then if you have an advance GE plus you could code your login and password so that you do not have to type it in also.
3. Once focus, have coordinates pasted in the correct place in GE. Have macro hit <return>.
Voila.
If you are not familiar with the macros in excel. You can fool around recording one and optimizing it after you have the obtain results.
Once you have it properly coded you assign a button to the macro.
You can highlight a series of cells with coordinates. (any number of cells)
And excel will trigger them to GE and put place marks automatically.
voila!