If I understand correctly, you want the results of a formula to show either a
negative or positive sign before the number... so if A1-B1 where a negative
2, it would look like this: -2 and if it were positive it would look like
this: +2.
If that's what you are looking for, select the range containing your results
and choose Format, cells, number tab. Select Custom as the number format
(it's at the end of the list) and enter this:
+#,##0.00;-#,##0.00;0.00
this custom format would display numbers with commas as needed, a decimal
and two decimal places, with a + for positive and a - for negative and 0.00
for results of zero. If you need your results to appear differently, change
the custom format accordingly.
For example:
+#,##0;-#,##0;0
would display with no decimal places, but with the positive and negative
signs... and zero would simply be 0.
Remember that formatting to reduce decimal places does NOT (usually) change
the value, only the appearance.
Good luck!