VBA to add a value to an excel cell at a defined row and column position

I am building a lookup list of temporary sheet names (in colA), and this code aims to add a new sheet name to bottomRow+1 (ie to append the sheet name to the list in colA).
In colB: False means the data in the respective temp sheet has not been changed; True means it has been changed.

Since the length of the list is dynamic, I chose to add sheet names to the list using a .Range(Cells) syntax. But I cant get it to function.

Here is my code, with a set of failed lines, using a dynamic cell range. The only thing that worked was the static .Range("A3"):

Dim bottomRow as integer
Dim rn_bottomRow as range

Set rn_bottomRow =    
            ThisWorkbook.Worksheets("TempList_Shts_VisioData").Range("A1").End(xlDown)
            bottomRow = rn_bottomRow.row  ' this identifies the last occupied row ok
 
            With Worksheets("TempList_Shts_VisioData")
                .Activate 'sheet IS activated
                .Range(Cells(3, 2)) = "hello"                              'this line failed      
                .Range(.Cells(bottomRow + 1, 2)) = "hello"       'this line failed  
                .Range(.Cells(3, 2)) = "hello"                             'this line failed  
                .Range(.Cells(rn_bottomRow.row + 1, 3)) = "False"     'this line failed  
                .Range(.Cells(3, 2)) = "hello"                             'this line failed                      
                 .Range("B3") = "False" 'this line worked but I need a dynamic cell reference!!!
            End With

Evidence that .with syntax is working:
 .Activate 'sheet IS activated:  TempList_Shts_VisioData becomes the active sheet
 .Name returned the correct sheet name

I cant fathom my error...
What is the correct syntax for Range using Cells property - for active and inactive sheets, respectively?

This code is written within a class module; does that matter?
An explanation of the principles behind a solution would be appreciated.

Thanks
Kelvin