I was having trouble getting the correct negative number format for a grid component for one of my clients. The client wanted the following format:

-$999,999.99 for negative numbers and
$999,999.99 for positive numbers

The standard negative formats are: ($999,999.99) or $-999,999.99.

After a bit of research and a lot of trial and error I came up with this for the "display format" for a number field in a grid component:

if(left(alltrim(str(<value>,16,2)),1)="-","-"+transform(abs(val(alltrim(str(<value>,16,2)))),"@t $$$,$$$,$$$"),transform(abs(val(alltrim(str(<value>,16,2)))),"@t $$$,$$$,$$$"))

It's kind of a combination of things I picked up from different posts viewed while researching negative number formats.
I thought I'd post it on the outside chance someone else might be looking for the same thing.