Inline Visual Basic .NET questions

I am converting some things from 2002/vb script to 2006/Inline Visual Basic .NET.

I notice that some of the functions I want to use are not available. 

For example if I create a class, I can access the “IsNumeric” function. But in the Inline Visual Basic .NET scriptoid, this function is not recognized. 

I can not find any reference or documentation on just what Inline Visual Basic .NET is and what it is limited to.  It seems to be a very limited successor to Visual Basic for Applications.

Am I missing something? This Inline VB doesn’t seem as useful as I had hoped.

Do I have to create an External Assembly to do any of the things I am used to in normal Visual Basic?  Is there any documentation available about Inline VB and what it is limited to?

If I create an external Assembly and Import external libraries, would they then be available to the Inline script?

Thanks