Thanks a lot Marinus and Anandvarma !

INDEX was exactly what I was looking for !

Finally I implemented that way and it works :

In my formula, I replaces the cell A2 by INDEX(A1:A3;2;1)

Formula INDEX(A1:A3;2;1) returns the content value of A2.

Here 2 is the #line, and 1 is the #column.

When I insert a new line between A1 and A2, A2 becomes A3, and formula becomes  INDEX(A1:A4;2;1)

Formula INDEX(A1:A4;2;1) still returns the content value of A2. What we wanted !! :D

Hope this helps !

See ya

JRC