help with a unique formula question

[RompStar]

Ok. I have a workbook, in this workbook there is a worksheet called:

main

on the main worksheet I have a import button that I press,
which fetches a daily roster file from the network and it imports the
files into the workbook into a sheet called:

master.xls

So there are two sheets: main and master.xls (with the .xls extention)

Before I go on to explain what I mean by help with a formula, let me
explain what the master.xls sheet has:

4 columns:

A11 headers, data starts at A2 and below.

Daparment Name, Date, Employee Name, HR status code

So for example, lets use these values, A22

SORT, 8/1/2005, Joe Smith, Present All Day

------------ so I hope I made that master.xls sheet clear,
it's basic :- )

Now, the main sheet is always there, master.xls is only there if I
press the import button, everytime I press the import button, the old
master.xls file is deleted and a new one imported in it's place.

Everyday I have to check to make sure Roster was updated for all the
departments, and right now I have to visually check it, scroll down,
find the date and manually look for the Department name to make a
match.

So on the main sheet, I wanted to make something simple that looked
into master.xls and quickly told me in the sheet of (main).

So on the main sheet, in cell:

B27 I have: SORT (formatted for text)
C27 I have the date using the =now() formula (formatted for date)

and in D27 I wanted to put in a formula that would, basically do this.

Look into B27 and C27 on (main), and then look into (master.xls) and
see if that Date and Department is there and if so, Print Yes or No
into D27, where the formula would reside.

Basically I wanted a formula to check to see if the updates were done
and I could just carry over the formulas for all the departments below
and quickly find out my answer.

From the research that I have done, I was told that I would have to

concatenate the columns, but I was wondering if it would be possible to
have it done without doing that ?

I was told that I could use an array formula but it never ended up
working, so not sure this formula was ok: here it is:

=IF(ISNUMBER(MATCH(B27&CHAR(160)&C27,master.xls!A:A&CHAR(160)&master.xls!B:B,0)),"Yes","No")

and I entered this formula using Control+Shift+Enter at the end (CSE)
since it is an array formula. I see {} so I know I entered it
correctly.

So not sure, if I did something wrong, or that formula not work, please
help me out, thanks.

A Great learning experiance this Excel has been.

If you have a difference formula or a different way of doing it, I
would like to hear it all, thanks.