TM1 TI process- Set Security based on CHILD ?

Last question of the week -- I want to execute some looping similar to the following PSUEDO -CODE:
If this possible: (sort of Backwards Cascade of Security)

vGroupsDim = '}Groups';
vDimCountGrp = DIMSIZ(vGroupsDim);
vIndexGrp = 1;
WHILE (vIndexGrp <=...