Let's say that you data is in columns A:F, and your 7th column is col G.  In cell H2 (I assume you
have headers), enter the formula

=NOT(ISERROR(MATCH(A2,$G:$G,False)))

and copy down column H to match columsn A through F, then copy all of column H to I:M.

Any FALSE values will show missing values from the corresponding row, offset by 7 columns.  (A False
in cell I23 means that B23 was not matched...)

HTH,
Bernie
MS Excel MVP

Two possibilities:

1.  (Which I think is faster, though I'm a programmer.)  Write a macro that
simply loops through the range of cells in the 6 columns and compares the
current cell in column 7 to the cells in the 6 columns.  If no match is found
in any column, it puts that column number into a string and at the end of the
search writes that string to an adjacent cell.  So the output would look
something like this:

A  B  C  D  E  F  G  H (H column is the column to report the misses)
                          A, D    <--  this string gets output by the macro
saying the value in G (whatever that happens to be) was not found in columns
A and D.

2. VLOOKUP - this would take 6 of them, 1 per column.  So using the above
picture, columns H-M would each contain a lookup of the value in column G (H
would check A, I - B, etc.).  You can wrap it with an IF statement so the
cell appears blank if it found a match and the column letter if it doesn't.  
Here's the formula for H:

=IF(ISNA(VLOOKUP(G1,A$1:A$100,1,FALSE)),"A","")

Copy this formula to I-M and down as many rows as needed (of course change
the 100 to be however many rows you need).