Workbook.open a filename with path and cell value in it

Complete script is:

Sub IMPORTEXAMPLE()
'
' IMPORTEXAMPLE Macro
'
'
    Sheets("DATA").Select
    Workbooks.Open FileName:="O:\Splitsen\TEST.xlsx"
    Cells.Select
    Selection.Copy
    Windows("SPLITSEN_v1.0g.xlsm").Activate
    Cells.Select
    ActiveSheet.Paste
    Sheets("HS lijst").Select
    Range("C4").Select
    Windows("TEST.xlsx").Activate
    Application.CutCopyMode = False
    ActiveWindow.Close
    Application.CutCopyMode = True
    Windows("SPLITSEN_v1.0g.xlsm").Activate
End Sub

The two lines in red have the text "TEST" stated but I want to change those to the text selected in cell J2.

@Norie sheet name and file name are is marked blue above.