VBA Excel-2010 How do you add data to an external workbook

Use variables to hold you workbooks and reference those

Dim wb As Workbook , path As String, wbOther As Workbook
path = "workbookpath"
Set wb = Application.Workbooks.Open(path)
Set wbOther = ThisWorkbook
wbOther.Worksheets("Sheet1").Range("A1") = wb.Worksheets("Sheet1").Range("A1")