boolean in a string use another language

Hi,

I have a problem,

as you can see in my comment, depending of the way I write a boolean in a string, the language of what is written change.  The problem I have, it's on my workmate's computer there is no problem.  The language of the string written is english.  I can't modify the code.  

So, I know how to debug the code, but do somebody can tell me advice to know how to look

Dim a As Boolean
Dim x As String

a = True

x = "hello " & CStr(a) ' -> hello true
x = "hello " & a       ' -> hello vrai


thank you