A hollow microcantilever is used instead of a conventional microcantilever to dispense and aspirate liquids in the femto-litre (10^-15 L) volume range in an atomic force microscope (AFM) setup. The inherent force sensing capability of the cantilever is used to monitor the fluid manipulation in-situ. At this small scale, parameters like: surface energy, evaporation, viscosity and temperature become important for controlled manipulation. In a conventional AFM, these parameters are usually not taken into consideration as feedback parameters. In the present work, we report initial experimental results on the dosing process and an analytical dynamic model of the process. The model is based on the liquid bridge between the cantilever tip and the substrate, which can describe the dosing process with variance accounted for (VAF) larger than 90%. We aim to use this model and implement a control system for precise dispensing and aspiration.