Hi surya,
I had a look at your attachment, you currently only have 2 sheets in there with "Calc" as the 1st part of the name - if there's only 2 sheets, the solution that Jacob gave you is more than adequate for your purposes, all you have to do is change "Sheet1", "Sheet2" to "CalcPre", "CalcPost" or whatever other name you care to give the sheets. If there are a couple more sheets like that, you just add their names to the case statement.
However, I'm going to assume that maybe there will eventually be many sheets added later with "Calc" as the first part of the name, and change the case statemant to an If statement so we can use wildcards:
Option Explicit
Private Sub Workbook_SheetChange(ByVal Sh As Object, ByVal Target As Range)
Dim Val1 As Variant
Application.EnableEvents = False
If Sh.Name Like "Calc*" Then
If Target.Column = 1 Then
Val1 = Evaluate(Target.Text)
If IsError(Val1) = True Then
Range("B" & Target.Row).ClearContents
Else
Range("B" & Target.Row).Value = Val1
End If
End If
End If
Application.EnableEvents = True
End Sub
HTH
John