I still don't understand your question.
The date in the database is a Decimal, and stores dates in YYYYMMDD format?
and you want to create a parameter TO and Parameter FROM that you can pass into the Dataset to pull correct records?
or
You have all the data set stuff figured out, and you just want to display the decimal value of YYYYMMDD from the dataset onto a tablix but show it in MMM/YYYY format?