Values to Schema Data Types

Good morning,

I'm using Microsoft XML, v4.0 in Visual Basic to manipulate my XML
documents.

One thing I would love to do is take basic VB datatypes like Double, Long,
String, and convert them to schema-permitted datatypes.

Are there any available tools that, for example, convert a Double to the
appropriate string for an xs:Decimal with TotalDigits=3? Or do I have to
roll my own?

-Adam