Dataset in Datalayer

[fcoomermd]

I have an application which has a:
Presentation Layer (includes some business logic)
Data Layer (includes some business logic)

Within the Data layer, I populate a dataset via a bunch of Stored Proc calls. Within the presentation layer, I call methods within the Data Layer which returns the dataset.
For example:
Presentation -
dim ds as new dataset
ds = datalayer.getDataset(customerNumber)

Data Layer -
getDataset(customerNumber as integer) as dataset
....

Is there any extra overhead for returning dataset (sometimes large) within multiple method calls?

I was thinking of having the dataset to be global either:
Within the datalayer and just call the reference to it, for example:
dim ds as dataset
ds = datalayer.dataSet

or return an instance of the dataset at the topmost level of the presentation layer, then make it global from there...

Thoughts? I want to seperate my data more from my presentation layer... I find it hard to do the seperation because a datase is so tightly bound, not to mention I am using binding...

Thanks for any help