Just read the topic "Interpolation" in the Labtalk Help - you can find some useful code samples there.
For instance, if linear interpolation sutisfies yor needs, you can use range variables as functions (copied from LT Help):
newbook;
wks.ncols = 4;
col(1) = data(1,0,-.05);
col(2) = gauss(col(1),0,.5,.2,100);
range rxy = (1,2);
rxy(.67)=;
range newx = 3; // Use column as X column data
newx = {0, 0.3333, 0.6667, 1.0}; // Create our new X data
range newy = 4; // This is the empty column we will interpolate into
newy = rxy(newx);
