Inno Setup Problem

[tim.calderwood]

Everything was working great in 4.6 then I upgraded to version 5.0. Now when the script tries to execute an inno setup with an option flag /d we get an IO error in Inno. I have determined that the problem is being caused by Visual Build and some extra text it is putting in. Here are the options for the INNO step.
FileName: C:\buildtools\Installer\Ascot5.iss" /dmtc
Specifiy .... filename: C:\Program Files\My Inno Setup Extensions 3\isppcc.exe

If I run this, the command line looks like this...
"C:\Program Files\My Inno Setup Extensions 3 isppcc.exe" "C:\buildtools\Installer\Ascot5.iss\" /dmtc"

The problem is Visual Build is putting in an extra "\" after .iss. I have tried adding a '"' to the begining of the line, but visual build removes it. I have tried taking out hanging quote, but then that gives me the following command line....
"C:\Program Files\My Inno Setup Extensions 3 isppcc.exe" "C:\buildtools\Installer\Ascot5.iss /dmtc"

The problem with is that INNO thinks the /dmtc is part of the file name.

If I remove the /dmtc, the script runs fine excet for the flag is missing to turn on some options in my setups.So, I am at a lost as how to fix this. The command line we need is...
"C:\Program Files\My Inno Setup Extensions 3
\isppcc.exe" "C:\buildtools\Installer\Ascot5.iss" /dmtc