I change to docmd command and it work the way you want..
Private Sub Command0_Click()
On Error GoTo Err_Command0_Click
Dim stDocName As String
Dim stLinkCriteria As String
stDocName = "subform"
DoCmd.OpenForm stDocName, acFormDS 'the acFormDS tells the form how to open your subform in datasheet view
Exit_Command0_Click:
Exit Sub
Err_Command0_Click:
MsgBox Err.Description
Resume Exit_Command0_Click
End Sub