如何通过数据表设置treeview的子节点

以下为本个编写的treeview 的子节点代码，运行时出错，提示异常代码0，出自nodes:element not found,由于本人新学习应用，不知道哪里不对，求高手指点
1 this.lineStyle= 1  && tvwRootLines
2 this.style= 7  && tvwTreelinesPlusMinusPictureText
3 this.ImageList=thisform.imagelist1

4  SELECT * FROM department WHERE subdir=0 INTO CURSOR bm_temp0
5  SELECT * FROM department WHERE subdir=1 INTO CURSOR bm_temp1
6  SELECT * FROM department WHERE subdir=2 INTO CURSOR bm_temp2
7  SELECT * FROM department WHERE subdir=3 INTO CURSOR bm_temp3

8  SELECT bm_temp0
9   this.Nodes.Add(,,ALLTRIM(bmmc),bmmc,1)   &&江苏飞船

10    SELECT bm_temp1
11    DO WHILE !EOF()
12           this.Nodes.Add(ALLTRIM(bm_temp0.bmmc),4,ALLTRIM(bm_temp1.bmmc),ALLTRIM(bm_temp1.bmmc),2)    &&飞船公司目录
13        SELECT bm_temp2
14        DO WHILE !EOF()
15            this.Nodes.Add(ALLTRIM(bm_temp1.bmmc),4,bm_temp2.bmmc,bm_temp2.bmmc,3)           &&key--部门名称
16            SELECT bm_temp3
17            SET FILTER TO ALLTRIM(parentname)=ALLTRIM(bm_temp2.bmmc)
18            DO WHILE !EOF()
19                this.Nodes.Add(ALLTRIM(bm_temp2.bmmc),4,bmmc,bmmc,4)
20               SKIP
21            ENDDO
22             SELECT bm_temp2
23            SKIP
24        ENDDO
25        SELECT bm_temp1
26        SKIP
27   ENDDO