But get [error attached as jpeg]. Point being, there needs to be some simple how-to guidelines rather than just another RFM.
We certainly do not intended to start providing support for VB .Net or C# programming. MSFT has already done that. Their documentation for managed code languages and the FCL is quite good and we already have more than enough to do helping WinBatch users learn and use the many features of the WIL language. We certainly do encourage users to experiment with creating dotNet assemblies but that comes with the expectation that they also have at least some fluency in the managed code language they are using.
I suspect the reason for your error
is covered in the 'manual' and very little to do with the fact that you are building an assembly on the fly. From the manual: "Both member overloading and the fact that WinBatch cannot query the object for type information before making a member call as it does with regular COM Automation references mean that the colon (:) type qualifier needs to be used more frequently on CLR object member parameters. Fortunately, WinBatch will take standard variant type names like BSTR, UI8, BOOLEAN, R8, e.g., and convert them to equivalent Framework types automatically. It will also automatically deduce the correct Framework type for variant variables passed as parameters to a member without needing to specify a type with the colon qualifier."
In your specific case, try adding
decimal: or
System.Decimal: to your method parameter so WinBatch can generate a method signature that matches that of your method's. By default WinBath converts floating point numbers to 'System.Double' and your method's signature specifies 'System.Decimal'. You would have the same problem if you were using an FCL class that required decimal input unless it had an overload that accepted doubles, of course.
Again your error has nothing to do we the fact that you created your own assembly other than you choice of method parameters and there is absolutely nothing wrong with that choice.