decompile an executable

help! a developer quit last month and took all his source code with him for an old legacy VB application. We need help decompiling the app so that we can make a few modifications. We have tried a few of the available decompilers with no success including these: * VBReformer (dies with an error code 6 - overflow) * VBDecompiler Lite by dotfix software - says unrecognized compiler If you think you can do it, let me know. I will send the executable and pay if you are successful. Thanks!