从不同的工作簿调用单元格引用

Question

我正在尝试将另一个工作簿中的两个不同工作簿的变量相乘，而下面的代码看起来一切都很好但是它不起作用...如果有人解决了这个问题，那就很感激

'PTC is WB1 cell reference and Outstval is WB2 Cell reference  
wkb.Activate
With wkb.Worksheets(1)                   
    .Range("C4").Formula = "= ( " & PTC.Address(True, True, xlR1C1, xlExternal) & "*" & Outstval.Address(False, False, xlR1C1, xlExternal) & " ) "
     lr = .Range("A" & Rows.count).End(xlUp).Row
     .Range("C4").Resize(lr - 1, 5).FillDown
     .Calculate                                                                 
End With