Automatic add & subtract

Hello all,

I had such great success with my last question that I am going to attempt
one last question which will save me plenty of headaches if answered.

I have designed a monthly tracking program that each employee enters the
number of work they complete in a month. We will call this an ‘activity
report’.

In the activity report, there is a monthly roll-up sheet that totals all the
work completed in that month (31 days) using numbers.

I have created a ‘base program’ that lists all employees at the top with the
same headings used in the monthly roll-up.

To eliminate the need for key punching the employees numbers attained each
month, I have placed links from the base program under each employees name
along side the headings.

The base program is in a folder.

Each month, the employees complete the number of each work type and punch
that number in the appropriate cell along side each heading. The monthly
roll-up page automatically totals the work for the month using sum formulas.

The employee sends this electronic activity report to their respective
supervisors and said reports are dragged into the folder containing the base
program.

When the base program is opened, the links ask me to update the totals which
it does.

Question: Is there a formula that will do the following;

o If the number in a cell in the ‘activity report’ is 0 (zero) , leave it as 0

o If the ‘activity report’ cell has a number greater than 0, add it to the
base in that cell

o If the ‘activity report’ cell has a number less than the number in the
base, subtract it from the number currently in the base.

A very big thank you to all that can help with this.

-Bad