vfp 动态列求和,该怎么处理

MYFORM = NEWOBJECT("C_FORM")
MYFORM.SHOW
READ EVENTS
RETURN 
DEFINE CLASS C_FORM AS FORM 
   AUTOCENTER=.T.
   CAPTION="表单求和示例"
   ADD OBJECT GRID1 AS GRID WITH TOP=((THISFORM.HEIGHT-THISFORM.GRID1.HEIGHT)/2)+20,LEFT=(THISFORM.WIDTH-THISFORM.GRID1.WIDTH)/2
   ADD OBJECT OPTIONGROUP1 AS OPTIONGROUP WITH TOP=6,LEFT=THISFORM.GRID1.LEFT,HEIGHT=28,BUTTONCOUNT=2,AUTOSIZE=.T.   

   PROCEDURE OPTIONGROUP1.INIT 
      WITH THIS
         .VALUE=0
         .OPTION2.TOP=.OPTION1.TOP
         .OPTION2.LEFT=.OPTION1.WIDTH+45
         FOR I=1 TO THIS.BUTTONCOUNT
             .BUTTONS(I).AUTOSIZE=.T.
             .BUTTONS(I).CAPTION=IIF(MOD(I,2)=1,"统计","退出")
         ENDFOR
      ENDWITH
   ENDPROC
   
   PROCEDURE OPTIONGROUP1.CLICK
      IF MYFORM.OPTIONGROUP1.BUTTONS(MYFORM.OPTIONGROUP1.VALUE).CAPTION=="统计"
         *----方法一，数值型字段A1....An
         GO BOTTOM
         IF ALLTRIM(内容)!="合计" &&判断是否进行过"合计"
            SUM TO ARRAY HJ &&字段数<255
            INSERT INTO TABNAME (内容)VALUES ("合计")
            FOR I=2 TO FCOUNT()
                REPLACE (FIELD(I)) WITH HJ(I-1)
            ENDFOR
         ENDIF
         *----方法二（SELECT SUM(字段名1),SUM(字段名5),SUM(字段名10),......FROM TABNAME INTO CURSOR LSB）
         *----数值型字段不是相连的，可以自己研究。
         MYFORM.GRID1.REFRESH
      ELSE
         MYFORM.RELEASE
      ENDIF
   ENDPROC

   PROCEDURE GRID1.INIT
      CREATE CURSOR TABNAME (内容 C(4),A1 N(4),A2 N(4),A3 N(4),A4 N(4)) &&字段数<255
      INSERT INTO TABNAME VALUES ("A",15,16,17,18)
      INSERT INTO TABNAME VALUES ("B",20,21,22,23)
      GO TOP
      WITH THIS
         .FONTSIZE=10
         .HEADERHEIGHT=28
         .RECORDSOURCETYPE = 1
         .RECORDSOURCE = "TABNAME"
         .ROWHEIGHT=24
         FOR I = 1 TO .COLUMNCOUNT
             WITH .COLUMNS(I).HEADER1
                  .ALIGNMENT=2
             ENDWITH
         ENDFOR
      ENDWITH
   ENDPROC
   PROCEDURE DESTROY
      CLEAR EVENTS
   ENDPROC
ENDDEFINE