Excel On MAC .xlsm File Corruption

[Licoule]

I'm sorry in advanced if this has been answered before. I couldn't find the answer in past threads.
I have an .xlsm file that calls the user name to help make a record of changes

Function GetUserNameMac() As String
    Dim sMyScript As String

    sMyScript = "set userName to short user name of (system info)" & vbNewLine & "return userName"

    GetUserNameMac = MacScript(sMyScript)
End Function

The file and code in questions works great on a single computer. However I'm trying to have to file based on a shared network drive. When I move the file on to the drive, it works fine. When someone makes a change then saves, it works fine. After that first change is made, the file becomes corrupt. I have found one or two possible fixes online, but Ive never gotten a wrong answer from this form, so I was hoping someone was familiar with this issue. The computers are running OS X Yosemite 10.10.5 and the Excel version is 2011 ver. 14.5.2