Rollup summaries in Deals for Custom Modules and PO's Module

Rollup summaries in Deals for Custom Modules and PO's Module

Hello,

I made a custom timecards module and related it to the Deals module. I'd like to create rollup summaries for hours.. is it possible to make new rollup summary fields that are developed from formulas derived by fields in custom modules? If not, I can try to write a deluge script.

Similar question - I noticed the PO's module isn't available in the rollup summary field. Is it possible to enable this?

Thanks!