In computing sciences (e-Sciences) we need computer power, excellent algorithms and programming power in order to solve scientific problems leading to discoveries and development of innovative new products. So far, the computer power and the computing algorithms have been developed incredibly, and have provided enormous contributions to e-Sciences and e-Productions. Problem solving environments (PSE) support the programming power in e-Sciences and e-Productions, and have been studied actively for a few decades. In this paper a distributed PSE, named D-NCAS is presented, and a computer-assisted mathematical modeling support is also discussed in D-NCAS, which helps users solve partial differential equation (PDE) based problems in scientific computing. The D-NCAS PSE inputs a problem description and outputs a program flow, a C-language source code for the problem and also a document for the program. Each PSE module is distributed on networklinked distributed computers. The PSE holds all the information of the problem: PDEs, discretization scheme, mesh information, equation manipulation results, designed program structure, variable and constant definitions and program itself. The PSE concept has been opening a new direction for the computer-assisted programming or development of scientific simulation programs or CAEs.