Open workbook as variable

Hi All

I am trying to run a macro but want to use the name of the open workbook to declare a variable
So in this case I want to replace ("BANK_Architect_Template.xls") with the open workbook name,


"Set T_Site = Workbooks("BANK_Architect_Template.xls").Sheets("ReportControl").Range("A1")
Dim TSite As String
TSite = T_Site.Offset(4, 3).Value"

Any help would be appricarted
Thanks
Karen