Any Excel guru can help me??

I have three sheets (Sheet1, Sheet2, Sheet3).

Sheet2 has Worksheet_activate(Macro) on it.
Let say, I'm working on sheet1,if I move to Sheet2, then,
Worksheet_activate in sheet2 will be activates, right?
My question is, how can I (if possible) to disable the
Worksheet_activate to run in sheet2 if I move from sheet3 to sheet2 ??
I just want the Worksheet_activate in sheet2 running, only if I move
from sheet1.
Thank you.