Matrix operations can also be used for this, but usually it isn't necessary and you can just use formulas. txnelson provided one very easy to understand version, here is other version
Column C
Col Cumulative Sum(!IsMissing(:Column 1)))
Column N
Col N Missing(:Column 1, :C))
or
If(IsMissing(:Column 1), Col N Missing(:Column 1, :C),.))
Can combine these into single one, but these tend to be difficult to understand
If(Is Missing(:Column 1),
Col N Missing(:Column 1, Col Cumulative Sum(!Is Missing(:Column 1)))
, .
);

-Jarmo