2 cell condition sheet/tab color change, and VBA copying with sheet

Sub colortabs()
    Dim B1 As Range, _
        J1 As Range

    Set B1 = Range("B1")
    Set J1 = Range("J1")
    
    If IsDate(B1.Value) And J1.Value = "" Then
        Sheets(1).Tab.Color = vbRed
    ElseIf IsDate(J1) Then
        Sheets(1).Tab.Color = vbGreen
    End If
End Sub

It worked as a standard code module with XL2007.

So I tried this on a brand new XL2010 as a standard module, and it worked fine after saving as a macro enabled workbook. The file I am trying to use this for is a decently large (4-5mb) binary file. It didn't seem to work for that file, though my above posted macro works like a charm. Do you happen to know why one macro would work in binary workbook and another would not?
EDIT: Well I figured this part out.. I didn't realize your code was specific to Sheet1 at first, and my spreadsheet didn't have a sheet named Sheet1

A few questions:
-Is there anyway to make this effect multiple specific sheets, but not all? (A single sheet will be copied approximately 500 times using my above macro, and I need this to effect all copies but nothing else) ..do you know if this macro will successfuly be duplicated through the use of my macro above (dynamic), or will it remain point at a single sheet even if it does copy as sheets are copied?

-Is there anyway to make this happen automatically each time excel does a calculation, rather than having to run the macro?

Thank you, again, protonLeah.

I tried the tab color macro in an xlsb and it worked (sheet change event).

The only way I can see to have the one macro work on multiple sheets easily is to put in the the "ThisWorkbook" module as a sheet change event. In order to have it work on some sheets but not all, it would be be easiest if the sheets you want it to apply to have something in common in the name that could be tested with an IF..THEN statement. Alternatively, you could list the sheets you want to bypass and exit the code. For example:

Option Explicit
Private Sub Workbook_SheetChange(ByVal Sh As Object, ByVal Target As Range)
    If Sh.Name = "sheet1" Then
        
        If Target.Address(0, 0) = "B1" Or Target.Address(0, 0) = "J1" Then
            Dim B1 As Range, _
                J1 As Range
        
            Set B1 = Sh.Range("B1")
            Set J1 = Sh.Range("J1")
            
            If IsDate(B1.Value) And J1.Value = "" Then
                Sh.Tab.Color = vbRed
            ElseIf IsDate(J1) Then
                Sh.Tab.Color = vbGreen
            End If 'is date
        End If  'target
    End If 'sh

End Sub