When you need to compare two strings in SQL to check if this string contains uppercase or lowercase values it is always a problem, because in sql "ExTremeDev.blogSpot.com23" is equal to "extremedev.blogspot.com23".
I also needed to do such thing, in order to make some rules for a password, so that it will contain numbers, uppercase characters and lowercase characters.
Here I will provide an example like that:
So to check if a string contains:
1) lowercase characters: @myString = LOWER(@myString) COLLATE Latin1_General_CS_AI
2) uppercase characters: @myString = UPPER(@myString) COLLATE Latin1_General_CS_AI
3) numbers: PATINDEX('%[0-9]%',@myString) = 0
The COLLATE here is doing all the Job, so do not remove it :)
About PATINDEX you can always find some information on Microsoft: http://msdn.microsoft.com/en-us/library/ms188395.aspx
I hope this will help others as it took some time for me to find this solution.