Excel 2000

I have a sheet I enter lots of data from check books into. I have many
Columns and at the end of each Coolum I have a Sum in each cell to check
that the data was entered correctly.

Example:

A1 I would enter ($45.00)
R1 I would enter $45.00
In X1 if there is no difference you see the - symbol so I know I entered
the two numbers correctly. X1 is set up so I know the two numbers match and
I didn't enter $45.00 in one row and $44.00 in the other.

After this sheet fills up a bit it takes to much time to scroll down to
check all these entries. Is there a code I could enter that would display a
message box telling me X1 had a value other than -. In other words if X1 is
greater than 0 (zero) I need to know right then so I can make the change as
I go.

All the best,
SG