To be honest i cant work out what you are trying to do, but if you want some kind of progress bar you can add a row count that shows on another sheet (this only show every 100 rows, but you can change that) - you will have to update your code so that the find and replace are working on the orginal sheet and not the 'Progress' sheet
Code:
Sub BulkReplace()
Dim Rng As Range, SourceRng As Range, ReplaceRng As Range
Dim rCount As Long '<New
Dim tCount As Long '<New
Dim aSheet As String '<New
aSheet = ActiveSheet.Name
On Error Resume Next
Application.ScreenUpdating = False
Application.Calculation = xlCalculationManual
Set SourceRng = Application.InputBox("Source data:", "Bulk Replace", Application.Selection.Address, Type:=8)
Err.Clear
If Not SourceRng Is Nothing Then
Set ReplaceRng = Application.InputBox("Replace range:", "Bulk Replace", Type:=8)
Err.Clear
If Not ReplaceRng Is Nothing Then
Application.ScreenUpdating = False
Worksheets.Add.Name = "Progress"
tCount = Worksheets(aSheet).Cells(Rows.Count, 1).End(xlUp).Row '<New
Worksheets(aSheet).Activate
For Each Rng In ReplaceRng.Columns(1).Cell
SourceRng.Replace what:=Rng.Value, replacement:=Rng.Offset(0, 1).Value
rCount = rCount + 1
If Int(rCount) / rCount = 1 Then '<New
Application.ScreenUpdating = False '<New
Worksheets("Progress").Range("a1") = rCount & "/" & tCount '<New
Worksheets("Progress").Activate '<New
Application.ScreenUpdating = True '<New
End If '<New
Next
End If
End If
Application.ScreenUpdating = True
Application.Calculation = xlCalculationAutomatic
End Sub