Having an issue with a Macro

I can't seem to figure out how to set a Macro that specifically re-rolls a one once not repeating. Can anyone help me with this?

From Dice Reference Rerolling Dice (B,F)  rCP Several systems require that certain dice be reroll, for example brutal weapons in D&D 4e require any 1s or 2s to be re-rolled and the original die value ignored. The reroll modifier can be specified multiple times to allow rerolling at multiple Compare Points. By default the dice will continue to reroll until the result is inside the defined parameters. Optionally you can set the results to only reroll once regardless of the outcome. Example Rerolls 2d10r<2  - Roll 2 d10's and reroll any time a 2 or lower is rolled 8d6r  - Roll 8 d6's and reroll any time a 1 is rolled 8d6r2r4r6  - Roll 8 d6's and reroll any time a 2, 4, or 6 is rolled 2d6ro<2  - Roll 2 d6's and reroll anything less than 2 but only once So you want something like the last roll, specifically ro  for your use-case.