Debug VB DLL passback

I am attempting to display data from a DLL written in VC 6 to an application written in VB6. To do this I have used a callback function to simply pass a string of text back to the VB application, which then appends the string to a rich text box in a form. Unfortunately this seems to have some issues, in that when I start clicking around the MDI form, or bring another window on my pc into focus the Data passing application will sometimes crash. I push a line of text onto a string in VB, from the DLL from inside a while loop that has a Sleep(1) in it, and then append the data every clock cycle of the VB. I don't want to have the DLL call an append command directly, because I want it to be running as fast as possible. I have made a stripped down version of my project and put it into a zip file. There is a VB folder and a DLL folder. The data passing display window is displayed below the control window. To start the data passing the user can just press GO, and STOP stops the data passing. There is a sample data file in the vb folder called [login to view URL] that I use as my test data file. The program will prompt you for it the first time you press GO. As stated above the text starts streaming out onto the display window, but if I start clicking around a lot or switching to other windows it will eventually crash. If anyone can figure out how to make this more reliable I would really appreciate it. When bidding please indicate whether you already have a fix or if you are bidding to attempt to debug. ## Deliverables 1) Complete and fully-functional working program(s) in executable form as well as complete source code of all work done. 2) Deliverables must be in ready-to-run condition, as follows (depending on the nature of the deliverables): a) For web sites or other server-side deliverables intended to only ever exist in one place in the Buyer's environment--Deliverables must be installed by the Seller in ready-to-run condition in the Buyer's environment. b) For all others including desktop software or software the buyer intends to distribute: A software installation package that will install the software in ready-to-run condition on the platform(s) specified in this bid request. 3) All deliverables will be considered "work made for hire" under U.S. Copyright law. Buyer will receive exclusive and complete copyrights to all work purchased. (No GPL, GNU, 3rd party components, etc. unless all copyright ramifications are explained AND AGREED TO by the buyer on the site per the coder's Seller Legal Agreement). ## Platform Win XP VC++ 6 VB6