One way:

   =IF(COUNTIF(DQ:DQ,DO1),"Match","No Match")

Another:

   =IF(ISNA(MATCH(DO1,DQ:DQ,FALSE),"No Match","Match")

select row DO and click Format->Conditional Formatting
select "Cell Value Is" and "equal to" and enter the following formula in the
box
=DQ1
Click Format and select an obvious background color like lime green
Click okay

every cell in DO that matches DQ will now be highlighted.

One other interp ..

Assuming source names in cols DO, DQ are running in row2 down

Place in DR2:
=IF(COUNTA(DO2,DQ2)<2,"",TRIM(DO2)=TRIM(DQ2))
Copy down to the last row of data in cols DO/DQ. Col DR will return TRUE if
the names match on the same row (using TRIM will disregard any extraneous
space/s), FALSE if they don't match & blank if data is incomplete for
matching (either both DO/DQ blank, or one of the cols is blank). You could
then easily apply autofilter on col DR (via Data>Filter>Autofilter), and
filter out TRUE cases from the autofilter droplist in DR1.

One more option for you. In Excel 2007, you can select both columns, go to
Conditional Formatting, Highlight Cells Rules, and choose Duplicate Values.
It will fill cells with duplicate values with color.