How to use Excel VBA Worksheet type objects?

Hey Guys,

What I'm trying to do is to create a random data generator to use in PowerBI.

I'd like to use a VBA created Worksheet object to store the data generated
but I'm getting the following error:
"Run Time Error 91: Object variable ow With block variable not set"

I've created the object with:
Dim OUTPUT as Worksheet

And then I try and assign value to some cell with:
OUTPUT.Cells(1,1).Value="Hello World"

I've seen example scripts assign existing sheets in the 'Microsoft Excel Objects'
list to a Worksheet type variable. Is this the correct use or can I have a Worksheet
type object exist independently from the 'Object' list.

Thanks.