Mutual excitations of diverse sample elements constitute a main problem in x-ray fluorescence analysis. Effective computers permit a comprehensive solution (see [1]) on the base of Sherman's equation [2] for x-ray yields, enhanced by interelement effects. Suclt an enhancement can be estimated on the level of a pocket calcidator by a very simple formula. The respectivemodel proceeds from a quasi-continuous transformation of the primary fluorescence radiation into the secondary fluorescence along its outgoing path, according to the cross sections involved in the attenuation. It does not contain an explicite two-collision treatment and consequently runs along the line of the ordinary single-collision approach of x-ray excitation. It is discussed for NiZn as a system, which is highly sensitive to interelement interactions.