I have a main sub that makes use of a Client class: creates an array with 100 000 Clients and loops over the array 100 times, each time setting a different random number to each Client.

Sub start()      Application.ScreenUpdating = False      Dim i As Long     Dim j As Long      Dim clientsColl() As Client     ReDim clientsColl(1 To 100000) As Client      For j = 1 To 100000         Set clientsColl(j) = New Client         clientsColl(j).setClientName = "Client_" & j          Application.StatusBar = "Getting client " & j          DoEvents     Next      Dim clientCopy As Variant     For i = 1 To 100         For Each clientCopy In clientsColl             clientCopy.generateRandom         Next          Application.StatusBar = "Calculating " & i          DoEvents     Next      MsgBox ("done")      Application.StatusBar = False     Application.ScreenUpdating = True  End Sub 

Client class:

Option Explicit  Dim clientName As String Dim randomNumber As Double   Public Sub generateRandom()     randomNumber = Rnd() End Sub  Public Property Get getClientName()     getClientName = clientName End Property  Public Property Let setClientName(value As String)     clientName = value End Property 

However, this code takes different times if run from different workbooks. Being run from the first workbook it takes about 35 seconds to complete, while running from the second workbook it takes about 4 minutes. What might be the reason behind this? The only difference between the workbooks I see is the first’s size is 22 Kb, while the second’s is 6 772 Kb.