using a loop to select a certain value of a combo box

You can use a While loop

https://support.smartbear.com/testcomplete/docs/keyword-testing/reference/statements/while-loop.html

and loop 'while mycomboboxvalue <> 'Australia' 

this will work if you are sure that Australia is in the combo box

if Australia might not be there, then you will have to add another value to check at the same time like the count of the combo box list