Listbox and combobox stopped working after Office 365/Excel 2013 upgrade

I have a macro I use to administer a spread sheet database of job numbers. We recently upgraded to Office 365 / Excel 2013 after which lost list box functionality. Basically I use the macro to open up another spread sheet with all the current job number details. These details are loaded into a list box and displayed. As multiple users may need to access the database the aim is to manage access and minimise contention. There are other macros in the suite that allow new jobs to be created, modified or archive but a the list does not populate I am no able to confirm if any of these have been affected. The list box code in my macro is below:

If permitteduser Then
Load UserForm1
CBox1Ct = 4
JobNoChk = 0
Do Until JobNoChk = ""
CBox1Ct = CBox1Ct + 1
JobNoChk = xlwb.Worksheets(JobsSheetName).Cells(CBox1Ct, 2)
Loop

'Set CBox1Ct to point to the last row of data
CBox1Ct = CBox1Ct - 1
UserForm1.ListBox1.List = xlwb.Worksheets(JobsSheetName).Range("B5:L" & CBox1Ct).Value
' close the workbook without saving
xlwb.Close False
Set xlwb = Nothing