Why is my code grabbing row number from the wrong Excel sheet

Question

My code is broken, I'm afraid. I'm going to open an Excel file, count the number of rows of data it contains, and then use that row number to copy the data into the Excel sheet where the code resides. However, it continues to take the sheet's row number from which the button with the code is located. Despite my best efforts, I can't seem to figure out what I'm doing incorrectly.

Private Sub BrewhouseDataAdd_Click()
    
    Application.ScreenUpdating = False
    Application.Calculation = xlManual
    
    ' Set username
    Dim UserName As String
    UserName = VBA.Environ("username")
    
    ' Set up destination
    Dim destination As Workbook
    Set destination = ThisWorkbook

    ' Get date for filename
    Dim dateFromCell As String
    dateFromCell = destination.Worksheets("Front Page").Range("E4").Value

    Dim dateForFileName As String
    dateForFileName = Format(dateFromCell, "YYYYMMDD")

    ' Create source workbook name
    Dim sourceFileName As String
    sourceFileName = "Brewhouse " & dateForFileName & ".xlsx"
    
    Dim sourceFilePath As String
    sourceFilePath = "C:\Users\" & UserName & "\censored\censored\Extract Waste"

    ' Set source workbook (False for "Update Links" and True for "Read-Only Mode")
    Dim source As Workbook
    Set source = Workbooks.Open(sourceFilePath & "\Data Import\" & sourceFileName, False, True)

    ' Get the total rows from the source workbook (using column B as this will only pick the relevant rows)
    Dim iTotalRows As Integer
    iTotalRows = source.Worksheets("Export").Range("B1:B" & Cells(Rows.Count, "B").End(xlUp).Row).Rows.Count
    MsgBox (iTotalRows)

The message box keeps returning 31, which is the number of rows with data in the destination sheet, but it should return the value 15.

Answer 1

I changed this:

iTotalRows = source.Worksheets("Export").Range("B1:B" & Cells(Rows.Count, "B").End(xlUp).Row).Rows.Count

To this:

iTotalRows = source.Worksheets("Export").Range("B1:B" & source.Worksheets("Export").Cells(Rows.Count, "B").End(xlUp).Row).Rows.Count