Variable contains same values (VBA)

To generate a mailing list, I've recognized that in my variable "To" is containing the same values test@test.com. The mailing list was defined in Visual Basic for Applications (VBA). Well, I'm considering how could I define a statement to check, when the variable has the same values then trim all duplicates. That means I need the variable to appear just one time in the mailing list.

For example:

To = test@test.com; name1@test.com; name2@test.com; name3@test.com; test@test.com; name4@test.com

Does anyone have an idea?