Enabling Slider's "snap to grid" feature with "Constant sum slider"

One of the solution is to use slider question only and add custom validation such that sum of all choices selected is 100

Hi rondev, thanks for your response
I've tried that before but am not sure if the Custom Validation feature for Slider questions allows me to specify a validation criteria based off the sum of numerical responses for each option (see below).
Custom Validation only allows me to specify criteria for a single choice only, not for multiple / all choices.
If i'm missing anything, or have misunderstood your comment, please feel free to let me know.
Thanks!

We have to use math opearation on the last text box i.e. lets say if you have 4 statements (A, B, C, D) then you will select the custom validation as A "Is Equal to" 100 - ( B + C + D ).
Instead of "100 - ( B + C + D )", you will put math operation their with piped text at place of B,C,and D.