decimal entities in ePub instead of character entities

Hi,

some eBook Shop were I wanted to publish my eBook asked that I should use decimal entities in ePub instead of character entities (named character entities?).

I was already searching and looking in the manual but couldn't find anything how to change this.

Is there an inbuilt function in calibre?

Can I do something with the input for calibre?

Help is really appreciated.

Thanks

PS: tried to search&replace in sigil - with   -> *
It said it replaced XXX times but instead nothing happend :(