Say you have Table A and Table B. If you add a column to Table A, there's no way that I know of for a column also to be added automatically to Table B's structure. But you can add the extra column to Table B manually too and then have the contents of that new column update automatically when you change the contents in the corresponding new column in A. Is that what you want?
To do that you could put simple formulas in the "receiving" table B that refer to table A. In a cell in table B type =, hop over to the source table A, select the source cell you want, and hit return.
Then, if the two tables have the same structure, you can take the formula in table B and fill down or right to pull other values from table A. If they have a different structure, you would insert the formula cell by cell.
Using AppleScript with the old Numbers there are ways to "push" data from one table to another and even, I think, create new tables and columns and fill them with values. But the new Numbers 3.0 does not support AppleScript.
SG