>DEFINE CLASS testclass as Session olepublic	
>PROCEDURE 	FormatPrice(myPrice as String) 				
>Parameters MyPrice
>*** rest of code
>EndProc
>EndDefine

Why are you declaring the parameter twice? Would this code work better:

DEFINE CLASS testclass as Session olepublic
PROCEDURE FormatPrice
Parameters MyPrice AS String
*** rest of code
EndProc
EndDefine

? alltrim(oVfpDll.FormatPrice(myPrice)

There is a ")" missing at the end of this command