Langmuir-Blodgett multilayers of a photoactive two-ring phthalocyanine have been assembled and excitation with a fast laser pulse used to create photocarriers on the conjugated rings. Applying an electric field perpendicular to the plane of the multilayer, in the - direction, interlayer electron tunnelling is measured giving a range of carrier motion that indicates that all the phthalocyanine layers are crossed. In a novel experiment, molecular bilayers and saturated organic molecules have been inserted in designed z locations in the multilayer structure. Electron transfer has been demonstrated to be blocked by the bilayers. That is, the electron transfer has been controlled at a nanometre level by molecular electronic design. The technique can in principle be extended to create electronic blocks which can be turned on and off by electric fields, or by light pulses, thus opening the way to molecular electronic devices.