This paper is focused on reducing the design time in a CAD framework environment by the optimal use of resources. A user-transparent load distribution system (Framework based LOad DIstribution System - FLODIS) is presented that enables a distributed execution of design tools over a heterogeneous network of workstations. The basic idea of the proposed algorithm is to allocate tools to workstations by using estimations about the required resources. These values can be obtained by user-defined tool characteristics, recorded previous tool executions and by methodology information provided by the framework. Compared with standard distribution approaches that use less information about the activities, experimental data show a significant average reduction (40-50%) of the tool execution time.