Thanks Jim,
Very simple fix, Since the way the measurements are taken I have multiple parameters that have repeated max date. It worked anyway. Below is the script I came up with, however i created another logical nightmare of picking which subset table has the most recent Part ID. Your solution was much more simple.
dt = data table ("XYZ");
// Get unique values
uVals = AssociativeArray(:Part ID << getValues) << getKeys;
// Make Subset Tables
for(g = 1, g <= NItems(uVals), g++,
r2get = dt << getRowsWhere(:Part ID == uVals[g]);
dt2 = dt << subset(Rows(r2get));
dt2 << setName("subset ");