Combination Of Pairs, Power And String

I have a string of n pairs and want to check various combination of that string.
Example: Pairs 58 78 15
Since I know I have 3 pairs (but it can be 2 or 4), I know the number of combination I want to test, ie 2 power 3 = 8 combinations. How can I program a code creating the various strings, ie 587815, 587851, 588715, 588751, 857815, 857851, 858715, 858751 ?

This is what I have so far (not much):


Public unique_pair 'number of pairs provided by another macro
Public mystring 'provided by another macro
Sub make_guess()

Dim number_of_combination, i
number_of_combination = 0


number_of_combination = 2 ^ unique_pair
For k = 1 To number_of_combination

'how to generate the various string ????

Next k
End Sub