Worksheet Activate Event doesn't fire

I've got a workbook with multiple worksheets A, B, C, etc. Sheet A is active when I save the workbook. In the workbook.open event, I say "a.activate" but it appears that this does not function as the sheet is already active?

If I say:

b.activate
a.activate

then the worksheet_activate event for sheet A fires.

Question is: Am I right about this and is there a more elegant way to trigger the activate event on sheet A than say switching to some other sheet and then back again?