Navigate between Spreadsheets

I want to write data on one sheeet, select the next (pre-named) tab and write the second part of the data there.
1. I write the tabs OnPreReport.
2. Then I write the data, but don't know the command to "Select this-or-that" tab.

This is what I have so far:

Report - OnPreReport()
IF PrintToExcel THEN BEGIN
 CREATE(Excel);
//sheeet 1:
 Workbook := Excel.Workbooks.Add(-4167);
 Worksheet := Excel.ActiveSheet;
 Worksheet.Name := 'Name1';
//--- sheet 2:
Worksheet:=Excel.Sheets.Add();
Worksheet:=Excel.ActiveSheet;
Worksheet.Name:='Name2';
END;