why gif in excel is getting bigger and bigger?

[roymesi]

I want to insert a gif file to an excell sheet.
I found the correct way and it does succeed:

Private Sub CommandButton1_Click()
myval = Shell("explorer C:\Documents and Settings\My Documents", 1)
End Sub

Private Sub Worksheet_Activate()
WebBrowser1.Navigate "c:\Baby_crawling.gif"
End Sub

The weird problem is every time I open the sheet, or switch back to the sheet of the gif, from another sheet, the drawing is getting bigger and bigger, while the gif stays the same!
i've disabled the design mode, and exit the control toolbox, but still!
help, someone?