An experimental configuration for evaluating the magnetic force microscopy (MFM) instrument response for known structures, such as that around current-carrying lines containing defects of simple geometry, has been developed. The configuration includes mechanisms for nulling electrostatic potential differences between the sample and probe, and for providing an in situ reference structure adjacent to the test structure. The reference structure is used to normalize the signal magnitude from the test structure. The instrumental response function was determined iteratively by comparing the forward convolution of the calculated magnetic response with the measured signal from a 10 mum wide, 110-nm-thick Cr/Au-on-SiO2, structure. This response function was then used in a maximum entropy method deconvolution of signals from a 10 mum wide line containing a 3 mum x 40 mum slot. Preliminary results show that meaningful relative quantification of the MFM signal amplitude can be achieved to within 10% and absolute current variations can be detected to at least 10%.