How can I make a formula dynamically relating to a cell on "my" left in Google Spreadsheet?

Question

Say I have two a table like this:

   Name    B    C    D
1  Joe     15  17  =B1-C1
2  Mike    25  22 (auto fill)

And I need to insert a column between C and D like this:

   Name    B    C    D      E
1  Joe     15  17   31    =C1-D1
2  Mike    25  22   34   (auto fill)

And I want the last column change to C1-D1. Every time I need to fill in myself. Is it possible to just say:

My value = My 2nd left cell - My left cell

Answer 1

Use offset, with the base point being the same cell in which you enter the formula. So, in D1 it would be

=offset(D1, 0, -2) - offset(D1, 0, -1)

When a new column is inserted between C and D, the above becomes

=offset(E1, 0, -2) - offset(E1, 0, -1)

which still has the meaning "My 2nd left cell - My left cell".