I don't think there is a way to do it for just a specific worksheet.
In sheet A (or sheet B) in the VBE:
Code:
Private Sub WorkSheet_Activate()
With Application
.Calculation = xlManual
End With
End Sub
Private Sub WorkSheet_Deactivate
With Application
.Calculation = xlAutomatic
End With
End Sub
This changes the autocalc for the entire workbook.
ie: When sheet B is activated, sheet A will autocalc with the rest of the workbook. When sheet A is activated, neither sheet will autocalc.