Sub-Formula Not Showing Negatives

Sub-Formula Not Showing Negatives

I have the attached budget tracker in a subform, and using the forumlar:
Abs(0+${Builds.Total Estimates}-${Builds.Total Invoices})
or
Abs(${Builds.Total Estimates}-${Builds.Total Invoices})

but it is not showing negatives as negatives. 

Is there a way to show the "-" or colour code negatives?