HELP Pls- intermittent compile error in module -

[sleepers]

i have a module that lets me look up a certain days available musicians depending on the code i give it... eg if i type in 1 in the worksheet specifies box then it will list only mondays etc.

This has worked great for quite some time but now is seeming to error randomly..

the code is like below

Function Concatsetday1(rng As Range, Item As String, Optional dte = True)
Application.Volatile
For Each ce in rng

when the error occurs i check the module and it has changed to

Function Concatsetday1(rng As Range, Item As =, Optional dte = True)
Application.Volatile
For Each ce in rng

i do not know what is causing the module to change by itself?? I have not seem a pattern that leads to this error - we just use f9 to update after we select the code for the day we wish to view

we are running xp - excel 2003 on a 3 pc network and share the file

Please any help would be great

thanks
Michelle