Innosetup error

Hii try to integrate the innosetup code but i've one error in this line:

//TODO: goto the version page at LimeLM and paste this GUID hereconst  VERSION_GUID = 'Paste GUID Here';




// functions for activationfunction IsActivated(versionGUID: WideString): longint;


The error is:Unknow type 'WideString'


Please helpme


Maurizio