GetActiveOLEObject('Excel.Application') - мож поможет

RTFM

Retrieves a reference to an IDispatch interface to a currently running, registered COM object.

Unit

ComObj

Category

COM utilities

Delphi syntax:

function GetActiveOleObject(const ClassName: string): IDispatch;

Description

GetActiveOleObject returns a reference to the IDispatch interface of the active object for the given class indicated by ClassName. ClassName is the programmatic ID for the class of the active object from the OLE running object table. GetActiveOleObject is used to access the OLE running object table. To add an object to this table, use the RegisterActiveObject API.

If either the the class object or the IDispatch interface are not successfully returned, an EOleSysError exception is raised.

И что трудно было F1 нажать?