I need to make sure each combination is made up of 3 distinct objects, a 1, a 2, and a 3.
Each time one of these objects is clicked, it's value goes into a holding variable.
So if the first holding variable is 1, and the second is 2, and the third is 3 (or any other variation of those three), I then add 1 to my 123combo variable, and a bonus is awarded.
But if the first holding variable is 1, and the second is 5, then the holding variables are all reset and the sequence has to begin again.
There are several of each object (1's, 2's, and 3's) on the layout at any one time, and each object can be selected. This means the player can chose x3 1's in a row, if they want to.
If I use the approach you've suggested (e.g a combo variable that I add 1 to every time one of the three items is selected). It would be possible for the player to select x3 1's, or 2's etc, and still receive a bonus. But that would not be correct in the game.