Specification of the magnetospheric field configuration is a crucial problem in all multi-spacecraft or satellite-ground comparison studies in which accurate mapping along magnetic field lines is important. Previous attempts of event-oriented modelling were based on either the magnetic field measured by a few magnetospheric spacecraft (Pulkkinen & al., 1991-1993) or the isotropic boundaries of energetic particles measured by low-altitude spacecraft (Sergeev & al., 1988-1993) We develop a new approach which allows the use of both high-altitude magnetic field and low-altitude particle boundary measurements as input data. This method, utilizing the modified T89 model as the external field model, can significantly improve in constraining the model free parameters. Using this new approach, we modelled the magnetospheric configuration for a number of substorm growth phase events and a few steady convection events. We found that previous modelling approaches (using magnetospheric data alone or ionospheric data alone) usually result in similar magnetospheric models if the utilized data set is sufficiently large. In some events of substorm growth phase and steady convection the model resolves a local thin current sheet at about X= - 10 Re with the X-lengthscale of a few Re. In some cases the model fit to the observations is not good enough indicating a need for further improvement of magnetospheric model.