Creating Identity Column for Local and Remote Location in SQL SERVER 2005

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SQL-Server-2005

SQL-Server

I am Creating a Billing system application which based on wed for remote user and windows based for Inhouse users
Bills generated from both ends
To Store the bill information i have created a table in sql server 2005
as Billmaster with identity (1,1)
Now problem i am facing is that if same identity is inserted from Remote as well as Inhouse user For eg. if Bill no 18 is inserted from Remote as well as Inhouse user Then at a time of merging the data it may cause the problem
I am using merge replication to transfer the data in both ways
I want bill number to be unique and not to be duplicated
What kind of identity should i used NewId()
Eg. 65D9F929-5BF0-4F19-9706-554958FAF0B1
doesnt look standard as far as Unique bill number is Concerned

Please suggest if you've any solution