我做了一个DLL。（刚接触DLL）但我运行时没有问题，但程序退出时就出错。(50分)

请问大家为什么呢？我做的这个DLL是一个将DBGRID里的数据导入到excel。
这是我的DLL代码，大家给看一下，DLL在调用后退出时应该注意什么问题吗？
library savetoexcel;



uses Windows, SysUtils, Classes, Graphics, Forms, Controls, Menus,
StdCtrls, Dialogs, Buttons, Messages, ExtCtrls, ComCtrls, StdActns,
ActnList, ToolWin,comobj,dbgrids,grids,Variants,db;


{$R *.res}
procedure savetoexcelfiles(dbgridname:Tdbgrid);
var
XLApp: Variant;
Sheet: Variant;
WordApp,WordDoc,WordParagraph,WordRange,WordTable:variant;
I, J: Integer;
SaveDialog:TSaveDialog;
pBookMark: TBookMark;
StrSaveFile:string;
IntFileType:integer;
SltRec,SltCol :integer;
ColIndex,RowIndex : Integer;
begin
if dbgridname.DataSource.DataSet.IsEmpty then begin
messagebox(application.Handle,'没有任何数据,不能进行保存',
'警告',mb_ok);
abort;
end;
SaveDialog:=TSaveDialog.Create(Nil);
SaveDialog.Filter := 'Microsoft Excel 文件|*.xls|Microsoft Word 文件|*.doc';
SaveDialog.Execute;
IntFileType:=SaveDialog.FilterIndex;
StrSaveFile:=SaveDialog.FileName;
if length(StrSaveFile)=0 then exit;
try
screen.Cursor:=crHourGlass;
case IntFileType of
1: begin
try
XLApp :=CreateOleObject('Excel.Application');
XLApp.WorkBooks.Add(-4167);
XLApp.WorkBooks[1].WorkSheets[1].Name := '导出数据';
Sheet := XLApp.WorkBooks[1].WorkSheets['导出数据'];
J := 1;
except
MessageBox(GetActiveWindow,'无法调用Mircorsoft Excel! '+chr(13)+chr(10)+
'请检查是否安装了Mircorsoft Excel。','提示',MB_OK+MB_ICONINFORMATION);
Exit;
end;
with Dbgridname.DataSource.DataSet do
begin
pBookMark := GetBookmark;
DisableControls;
for I:=0 to dbgridname.Columns.Count-1 do
begin
if dbgridname.Columns.Visible=False then
Continue;
Sheet.Cells[J,I+1] := dbgridname.Columns.Title.Caption;
end;
Inc(J);
First;
while not Eof do begin
for I:=0 to dbgridname.Columns.Count-1 do begin
if dbgridname.Columns.Visible=False then
Continue;
Sheet.Cells[J,I+1] := trim(dbgridname.DataSource.DataSet.Fieldbyname(dbgridname.Columns.FieldName).asstring);
end;
Inc(J);
Next;
end;
GotoBookmark(pBookMark);
FreeBookmark(pBookMark);
EnableControls;
end;
XLApp.activeworkbook.saveas(StrSaveFile);
Application.ProcessMessages;
XLApp.Application.Quit;
end;
2: begin
try
if VarIsEmpty(WordApp) then
WordApp := CreateOleObject('word.Application');
WordDoc := WordApp.documents.add;
WordParagraph := WordApp.activedocument.paragraphs.add;
WordRange := WordParagraph.range;
WordRange.Font.Size := 15;
WordRange.Font.Name := '宋体';
except
MessageBox(GetActiveWindow,'无法调用Mircorsoft Word! '+chr(13)+chr(10)+
'请检查是否安装了Mircorsoft Word。','提示',MB_OK+MB_ICONINFORMATION);
Abort;
end;
SltRec:=dbgridname.SelectedRows.Count;
SltCol := 0;
for j := 0 to dbgridname.Columns.Count-1 do begin
if dbgridname.Columns[J].Visible then
SltCol := SltCol +1;
end;

WordRange := WordApp.ActiveDocument.Content;
WordTable:= WordApp.activedocument.tables.add(WordRange,SltRec + 1,SltCol);
ColIndex := 1;

for j := 0 to dbgridname.Columns.Count-1 do begin
if (dbgridname.Columns[j].Visible = false) then
Continue;
WordTable.Cell(1,ColIndex).Range.InsertAfter(dbgridname.Columns[j].Title.Caption);
ColIndex := ColIndex + 1;
end;

RowIndex := 2;
ColIndex := 1;
with dbgridname.DataSource.DataSet do begin
First;
pBookMark := GetBookmark;
DisableControls;
while not Eof do begin
for j := 0 to dbgridname.Columns.Count-1 do begin
if (dbgridname.Columns[j].Visible<>false) then
begin
WordTable.Cell(RowIndex,ColIndex).Range.InsertAfter
(dbgridname.DataSource.DataSet.Fieldbyname(dbgridname.Columns[j].FieldName).asstring);
ColIndex := ColIndex + 1;
end;
end;
RowIndex := RowIndex + 1;
ColIndex := 1;
Next;
end;
GotoBookmark(pBookMark);
FreeBookmark(pBookMark);
EnableControls;
end;
WordApp.activedocument.saveas(StrSaveFile);
Application.ProcessMessages;
WordApp.Application.Quit;
end;
end;
Finally
SaveDialog.Free;
screen.Cursor:=crDefault;
end;
end;
exports
savetoexcelfiles;

begin
end.