You can create a custom user action in .NET:
http://www.visualbuild.com/Manual/userdefaction.htm
and use that action from your build scripts. The action code will still need to be maintained in a separate .NET project, but that may be preferable anyway since you can also step into your code to debug it in your development environment.
Unfortunately, there is no .NET equivalent to the Active Scripting interfaces MS defined for COM scripting, so there's no easy way to create .NET "scripts" that integrate into VBP in the same way (have access to global named VBP objects, can return expression values within fields, provide detailed error information with combined step, project, global, system script fragments, etc.). First, there was VSA [1], which is now deprecated, supposedly VSTA [2] is the replacement, but that is still in development.
We are considering offering an alternative to custom actions in a future release (possibly the ability to edit and execute .NET code from the Run Script action with some way to access the same global VBP objects that are available to Active Scripting engines).
Also, you aren't limited to just VBScript for scripting. You could use Jscript, Perl, Python, or Ruby instead, since Active Scripting engines are also available for those languages:
http://www.mvps.org/scripting/languages/
[1]
http://www.eggheadcafe.com/ng/micros...st23279439.asp
[2]
http://blogs.msdn.com/pstubbs/archiv...14/466165.aspx