I don't think there's a provided way to migrate VBA to .NET, but there are conversion tools online that might help as a syntactical reference for parts of the code. This approach will be cumbersome, but it might still be easier than doing it all by hand.
Here's an article that discusses migrating VBA to VB.NET:
http://msdn.microsoft.com/en-us/library/aa192490%28v=office.11%29.aspx
Converters
Here's a VB.NET to C# converter:
http://www.developerfusion.com/tools/convert/vb-to-csharp/
And here's another one:
http://converter.telerik.com/
I don't know how helpful the converters will be since they're designed to convert .NET languages to other .NET languages, but seeing as how VBA and VB.NET do share some similarities, you might be able to use the converter for some of the code.