How to Add a new record to an entity on adding a record to a subgrid

Hi,

we have a requirement that we need to add a record to an entity when we add a record to a subgrid using the (+) button.

1. We have a subgrid on opportunity record

2. Plus (+) button on the subgrid adds the contacts to the grid.

Now we want to add another record to a custom entity along with the above record addition to the subgrid.

Is there a a way that we can achieve the above functionality? Please suggest.

Thanks,

Venu