I don't really use projects, but this can give you one idea for the script using Data table subscripting (it assumes both have same amount of rows and columns)
Names Default To Here(1);
dt = New Table("Untitled 2",
Add Rows(3),
Compress File When Saved(1),
New Column("Column 1", Character, "Nominal", Set Values({"A", "B", "C"})),
New Column("Column 2", Numeric, "Continuous", Format("Best", 12), Set Values([1, 2, 3])),
New Column("Column 3", Numeric, "Continuous", Format("Best", 12), Set Values([4, 6, 8]))
);
dt2 = New Table("Untitled 2",
Add Rows(3),
Compress File When Saved(1),
New Column("Column 1", Character, "Nominal", Set Values({"A", "B", "C"})),
New Column("Column 2", Numeric, "Continuous", Format("Best", 12), Set Values([2, 3, 4])),
New Column("Column 3", Numeric, "Continuous", Format("Best", 12), Set Values([8, 12, 18]))
);
dt3 = dt2 << Subset(All Rows, Seleted Columns(0));
cont_cols = dt2 << Get Column Names(Continuous, "String");
dt3[0, cont_cols] = dt3[0, cont_cols] - dt[0, cont_cols];
-Jarmo