Reference Cell In Different Worksheet with Macro

[cgsoc11]

Alright so what I'm trying to do is standardize a workbook. I want to reference a cell in sheet 21. The way the formula is currently set up, it looks at cell A100 in the current active sheet. I want the macro to reference cell C3 in sheet 21 or my input sheet.

Here's the code

Sub CompanyHeaderChangeHorizontalSheet() 
     ' inserts the same header/footer in all worksheets
    Dim ws As Worksheet 
    Application.ScreenUpdating = False 
    For Each ws In ActiveWorkbook.Worksheets 
        Application.StatusBar = "Changing header/footer in " & ws.Name 
        With ws.PageSetup 
            .CenterHeader = _ 
            "&""Arial,Regular""&18&K000080                                                                                         &U&K000080" & Range("a100").Value 
        End With 
    Next ws 
    Set ws = Nothing 
    Application.StatusBar = False 
End Sub 

Thanks for your help!

[AAE]

Change

Range("a100").Value 

To

worksheets("Sheet21").Range("C3").Value 

However, I would opt to use the [URL="http://www.ozgrid.com/VBA/excel-vba-sheet-names.htm"]sheet code name[/URL]rather than worksheet name

Sheet21.Range("C3").Value