To generate 5 unique random values between 1 and 20, do this:

[lasso_Comment]

// fill a list with all values of the desired range
[loop: loopfrom='1', loopto='20']
	[List_AddItem: 'source_values', (LoopCount)]
[/loop]

[loop: '5']
	// get a random number from 1 to the count of unused values
	[var_set: 'random_pointer'=(RandomNumber:
		min='1',
		max=(List_ItemCount: 'source_values'))]

	// get the value at the position of the random number
	[List_AddItem: 'random_values',(List_GetItem: EncodeNone, 'source_values',
			ListIndex=(var: 'random_pointer', EncodeNone))]

	// remove the used value from the source list to prevent it from being used again
	[List_RemoveItem: 'source_values',
		ListIndex=(var: 'random_pointer', EncodeNone)]
[/loop]

[/lasso_Comment]

You have the five resulting random values in the list random_values. They are all unique.
