How to update DirectShow filter properties?

[Vaclav_]

I need some basic COM / DirectShow help.
I am using the EZrgb24 filter. No problems rendering it.
I am trying to update filter properties (HRESULT CEZrgb24Properties::OnApplyChanges()).
I have managed to retrieve them using the attached code.
I semiunderstand the ISpecifyPropertyPages interface, but have no idea how to access the CEZrgb24Properties::OnApplyChanges()).
I have been unable to find C++ sample code for updating filter properties.
Any hit will be greatly appreciated.

IBaseFilter \*pFilter = 0;
ISpecifyPropertyPages \*pProp;
HRESULT hr = pDocument->pC\_Graph->gcap.pTransferFilter->QueryInterface(IID\_ISpecifyPropertyPages,
	(void \*\*)&pProp);
if (SUCCEEDED(hr)) 
{
    // Get the filter's name and IUnknown pointer.
    FILTER\_INFO FilterInfo;
    hr = pDocument->pC\_Graph->gcap.pTransferFilter->QueryFilterInfo(&FilterInfo); 
    IUnknown \*pFilterUnk;
    pDocument->pC\_Graph->gcap.pTransferFilter->QueryInterface(IID\_IUnknown, (void \*\*)&pFilterUnk);

    // Show the page. 
    CAUUID caGUID;
    pProp->GetPages(&caGUID);
    pProp->Release();
    OleCreatePropertyFrame(
        0, //hWnd,              // Parent window float above all 
        0, 0,                   // Reserved
        FilterInfo.achName,     // Caption for the dialog box
        1,                      // Number of objects (just the filter)
        &pFilterUnk,            // Array of object pointers. 
        caGUID.cElems,          // Number of property pages
        caGUID.pElems,          // Array of property page CLSIDs
        0,                      // Locale identifier
        0, NULL                 // Reserved
    );
}