SendKeys To Dialog Box In External Application

I am automating 3rd party simulation software. The simulation is contained in a DLL. The DLL is programmed to interface though Excel. (Yes I have tried to use the dll outside of Excel, but other factors don't allow it. I have also asked the author to capture the error and recompile the dll)
VB.NET Application
- Excel.exe
-- Simulation.dll

Sometimes a runtime error occurs in the DLL and a dialgo box is created. "On Resume Next" in excel does not bypass the error, nor can I trap this error in the VB.NET application. Currently, if the simulation does not complete in 5 seconds (the DLL error has been thrown and a dialog box is present), I terminate excel application in the following pseudo code manner:

1) Excel.Quit (quit method of the Excel application object model; does not close excel, no error thrown)
2) FinalReleaseComObject() (for all the object references to Excel, workbooks, ranges, etc) <- a
3) Set all excel references to nothing
4) System.Diagnostics.Process.GetProcessById(MyClass.procID).Kill()

A RaceOnRCWCleanup is detected (An attempt has been made to free an RCW that is in use. The RCW is in use on the active thread or another thread. Attempting to free an in-use RCW can cause corruption or data loss.) when releasing the Excel application (the other object references do not cause this warning). Is this caused by Excel still being open? I have tried to "find" the error dialog box and close it with some SendKeys, but the an System.InvalidOperationException is thrown: SendKeys cannot run inside this application because the application is not handling Windows messages. Either change the application to handle messages, or use the SendKeys.SendWait method.

I have tried:
1) MyClass.xla.Dialogs.Application.SendKeys("{ESCAPE}")
2) MyClass.xla.Application.SendKeys("{ESCAPE}")
3) MyClass.xla.SendKeys("{ESCAPE}")
4) System.Windows.Forms.SendKeys.Send("{ESCAPE}")
5) My.Computer.Keyboard.SendKeys("{ESCAPE}", True)
6) sending keystrokes to buffer: [URL]
7) Creating a VBS file to send the escape character (doesn't work becuase of the path lenght)

This is what I know about the dialog box from Spy++:
Caption: run-time error
Class Name: #32770 (Dialog)
This program will be running un-attended so I want all debug errors and messages accounted for in code before this goes into production.