automation error for worksheets selection|VBA & Macros|Excel Forum|My Online Training Hub

I've a script to copy a formula from cell A15 of worksheet "Onepage" and past it onto a specific cell of the rest workseets starting sheet #4. It has been running smoothly for qute a long time. However, after making some chanages to my workbook last weekend without touching VBA at all, an automation error as highlighted below in red color came to me. May I know what's the problem and how to solve it? Many thnaks.

Sub UpdatePrice1()

Dim WS_Count As Integer
Dim I As Integer
Dim pos As Long

Application.ScreenUpdating = False

Sheets("Onepage").Select

pos = Date - 44560

Range("A15").Select

Selection.Copy

WS_Count = ActiveWorkbook.Worksheets.Count

For I = 4 To WS_Count

Worksheets(I).Select

Range("B" & pos).Select
ActiveSheet.Paste
Next I
Sheets("Onepage").Select
Application.CutCopyMode = False

Application.ScreenUpdating = True

MsgBox "Prices updating..."

End Sub