Excel 2010 :: Macros No Longer Work When Workbook Shared

Using Excel 2010.

I've created a spreadsheet at work that has two summary tabs which contain hyperlinks to around 30 separate sheet tabs.

On each sheet tab there is a list of unique values in column A (and other information relating to each value in columns B to D which are repeated for more than one unique value). In column E, users enter a test script name against each unique value they wish to 'reserve', and the macro picks out the unique test script names and via the COUNTIF formula counts the frequency of each test script name for each of the different values in column B.

My problem is that the macro seems to work fine if the workbook is not shared, but errors if the workbook is saved as shared. The error is 'Run time error 1004 - Unable to select the MergeCells property of the Range class'.

Here is the macro code:

Sub Get_Policies_Per_Script(updCol As Long, ShtName As String)
Dim rowctr As Long
Dim tgtrow As Long

Const ppsformula As String = "=COUNTIFS($A$3:$A$65000,I$24,$E$3:$E$65000,$G"

If updCol = 5 Then 'test name column has been modified

[Code] ..........