[excel] Excel VBA, How to select rows based on data in a column?

The easiest way to do it is to use the End method, which is gives you the cell that you reach by pressing the end key and then a direction when you're on a cell (in this case B6). This won't give you what you expect if B6 or B7 is empty, though.

Dim start_cell As Range
Set start_cell = Range("[Workbook1.xlsx]Sheet1!B6")
Range(start_cell, start_cell.End(xlDown)).Copy Range("[Workbook2.xlsx]Sheet1!A2")

If you can't use End, then you would have to use a loop.

Dim start_cell As Range, end_cell As Range

Set start_cell = Range("[Workbook1.xlsx]Sheet1!B6")
Set end_cell = start_cell

Do Until IsEmpty(end_cell.Offset(1, 0))
    Set end_cell = end_cell.Offset(1, 0)
Loop

Range(start_cell, end_cell).Copy Range("[Workbook2.xlsx]Sheet1!A2")