Software for converting 2.5D objects into STL and or STEP files. - repost 2

I have a program that produces components in a 2D format with an assigned height over many of the surfaces. I need a program that will read that data and convert the data into STL and STEP files. Currently we are producing AutoCad data for these files (DXF format). I have provided example files designating the data of relevance for someone as well as a few sample files. I expect extensive add on work from this project if all goes according to plan. So being able to read instructions and communicate clearly are important. I would like to develop a long term arrangement for creating 3d files and work for my small company. The project must be able to be run from within Visual Basic 6 (not .NET). being in native VB6 will seriously shorten the effort since no import capability from the ASCII file would need to be written, but the data could be streamed to you directly from VB. It may be expanded to the creation of a master STL file with several variations with in it to allow for multiple exports of the same type of part with minor adjustments to the size and features. Eventually we will be interested in a viewer for this data as well. This should not be quoted, but should be anticipated in code.