Hi,

before drawing the line, check that the coordinates are not in the fixed area.

For not drawing in the fixed row, this check is needed:

                if (y1 > _flex.Rows[0].HeightDisplay)
                {
                  formGraphics.DrawLine(myPen, x1, y1, x2, y2); //col1,row1,col2,row2  
                }

Same must be done for the fixed col.

Probably you will need more work if you want to clip the line instead of not drawing it at all. This task is up to you

Best regards

Wolfgang