Hi
Now I think I understand what you are trying to do. However MS Project is designed to manage progress against a pre-determined timescale for each task. Whilst there is a "manual" way doing what you want in MS Project I dont see any value in it. You are using Excel in this way which is a far better way of achieving what you want do do.
In Excel to pick up the last value in a row I would use the following formula:
=LOOKUP(9.99999E+307,H2:P2,H2:P2)
This will only display the last value in the row H2 to P2. The range can be changed to suit what you need.
Hope this helps.

Good luck.
Tony (OTPM)