The cross section of the diffractive process e(+)p -> e(+) Xp is measured at a centre-of-mass energy of 318GeV, where the system X contains at least two jets and the leading final state proton p is detected in the H1 Very Forward Proton Spectrometer. The measurement is performed in photoproduction with photon virtualities Q(2) < 2GeV(2) and in deep-inelastic scattering with 4GeV(2) < Q(2) < 80GeV(2). The results are compared to nextto- leading order QCD calculations based on diffractive parton distribution functions as extracted from measurements of inclusive cross sections in diffractive deep-inelastic scattering.