Find two row difference and store as third row.

Hi,

I want to find difference between two rows of a table and insert the difference value as third row in the same table. If the first row value is less than second row then the difference should appear within parenthesis instead of negative symbol.

Ex:

Name Service1 Service2 Service3 Service4

xxx 98 70 50 85

yyy 50 90 35 105

Diff 48 (20) 15 (20)