Manipulate Values & Formatting In Closed Workbook

I have 2 workbooks, one containing all my code and userforms and another containing all my data (which is continuously updated/ dynamic). I want to be able to manipulate the data without ever opening the workbook (at the moment I use the open workbook method, but it is extremely slow). I have found some code (Jwalk) which I think meets my needs (and is instant). I have adapted this so it points to a specific path rather than the active path as below etc. but I need to adapt it further so that:

1. When the data is opened it is formatted exactly the same as it is in the original sheet which includes any coloured cells, bold fonts, cell width, height and so on

2. Any changes I make can be saved back to the original sheet in the closed workbook.

3. The data always opens in a named specific worksheet i.e. "TempSheet" which sits in the workbook containing the code (my code is called from a userform within this workbook).

The code I am using from Jwalk is as follows:

Sub GetDataDemo()

Dim FilePath$, Row&, Column&, Address$

'change constants & FilePath below to suit
'***************************************
Const FileName$ = "Book1.xls"
Const SheetName$ = "Sheet1"
Const NumRows& = 10
Const NumColumns& = 10
FilePath = ActiveWorkbook.Path & ""
'***************************************

I am still learning VBA and can adapt/write small pieces of simple code, I have tried incorporating the paste special method, but in all honesty, don't know what I am doing and it results in lots of errors. Can anyone help me get this working/point me in the right direction? Also, what does 'Const' do? how do I bring in the data without specifying the number of rows, as this will be different every time?