OLE Automation, Variants and Delphi

We tried to use Variants to call Excel using OLE Automation.
All It's OK, bu we have to create an instance of Excel every time we need to
access to it.
How can we check if Excel is already running (this is simple) and get the
variant that points to it (or a pointer to Excel's IDispatch interface)?

Thank you in advance.

Massimiliano Trezzi,
INTESA Srl