Run-Time error 9 subscript out of range

Hi,

have the code below but getting "run-time error '9' Subscript out of range"


here is the code:

Sub SaveCurrent_Workbook()
Dim wbstring As String
 
wbstring = ActiveWorkbook.Sheets("STATEMENT").Range("SUBJECT").Value
Workbooks(wbstring).Save
End Sub

Thank you,