RagDyeR:

When formatting a cell, it doesn't matter where the data came from (Vlookup,
Offset, or any other formula). It only matters what the resulting data is.

I'm also having a hard time understanding why you would want a date *and* a
percentage in the same cell, but regardless, here are some pointers.

Excel is displaying your negative percentages without a sign because you told it
to. The format m/dd/yy;0.00% means "if the number in the cell is positive, use a
format of m/dd/yy; it it's negative, use 0.00%". The semicolon is what separates
the format for positive numbers from negative numbers. It's most commonly used
to display negative numbers in red.

In your case, you want something different. If the number is a percentage, you
want the 0.00% format. If it's a date, you want the date format. You now have to
tell Excel how to tell the difference. Fortunately, percentages are very low
numbers, and dates are much higher numbers. Depending on the highest percentage
you could ever have, you could, for example, tell Excel to format everything
less than 10 (ie, 1000%) as a percentage, and everything else as a date, with
the following:

[<10]0.00%;m/dd/yy