mouse buttons

Hi all, is there a way to change the default buttons from 4-5 on left and 4-5 on right? I wish the right ones were 6-7 or just different from the left. I tried to assign the buttons in a game but when 4 and 5 are assigned the other 2 become already used since they are both labelled the same numbers, so essentially I only have 2 buttons available instead of 4. Am using a viper 8k - have tried in synapse but can’t seem to accomplish what I want. Is there a solution? Thanks for any and all help.