Q:

is there any function to generate a UNIQUE string or UNIQUE number?

I need for function to generate a UNIQUE string, like:

DIM uniStr as string =
  generateUniStr()

is there any function already do this ?

A:

You can use 
Dim uniStr = Guid.NewGuid().ToString()

A:

You can gen up a GUID and stringify it.
You might want to give more details on what you're really looking for, because it's likely there's a better solution.

