Subscript out of range on other computers

Hey all,
I have a VB macro that works on my computer and have the error when running on other computers. I know the line of code that throws an error but don't know how to rephrase it to work on other computers in the network. The red shows what the debugger caught. THere are obviously several lines similar to this one, but what should I call the sheet then? Thanks!

If UserForm1.MultiPage1.Pages("page2").Frame2.CheckBox1.Value = True Then
        mwb.Sheets("51.5").Copy wb.Worksheets(1)
    End If

yes, they just run the same workbook that i copy to the network drive...maybe that isn't what you're asking.