Sometimes in the spectroscopic applications parasitic featureless base line is superimposed over useful signal from the measured sample. In this case you may need to subtract this base line manually from the measured spectrum. With DM2003 it is very easy because it includes specially designed tool - Base Line Subtraction (see screenshot below).
First you should plot data to be processed since this tool works only with active plot serie, then run Base Line Subtraction tool. You will see a set of buttons (HTML application) loaded into Browser window and your data plotted in a new temporary data window.
Press "Add spline points" button and then click plot area to add node points (at least six) that will belong to the base line as shown on the screenshot (red "x" crosses). You can move these points using point editor tool, or delete individual points (use point eraser tool) or whole array of points (click "Clear spline points" button). Use Zoom and UnZoom commands (or Axis Properties dialog box) to change plot scale. Notice that if you select any plot tool, "Add spline points" button will unselect.
Click "Subtract spline" button to create cubic spline curve that connects defined points and display the subtraction result.
If you wish to edit base line, click "Continue edit spline" link to show original curve and spline and go to point 1. Click this link again to show or hide the result curve.
Finally, click OK button to add column with the residual curve to the worksheet referenced by source curve or add spline curve itself if you check "Insert Spline" flag. Note that OK and "Subtract spline" buttons are disabled until you create valid base line.