.
The following could most likely be condensed some more / cleaned up some more .... but this works :
Private Sub CommandButton3_Click()
Dim WB As Workbook
Dim FileName As String
Dim FileName2 As String
'Getting file path and file name from the textbox
FileName = Sheet1.TextBox1.Value
FileName2 = Sheet1.TextBox2.Value
'Open the Excel workbook
Set WB = Workbooks.Open(FileName)
'Open the Excel workbook
Set WB = Workbooks.Open(FileName2)
Application.ScreenUpdating = False
'Workbooks.Open FileName:=TextBox1.Text
'Workbooks.Open FileName:=TextBox2.Text
Windows("fdatabase.xlsx").Activate
Sheets("Database").Range("C2").Select
'Cells.Find(What:="ID", After:=ActiveCell, LookIn:=xlFormulas, LookAt _
:=xlPart, SearchOrder:=xlByRows, SearchDirection:=xlNext, MatchCase:= _
False, SearchFormat:=False).Activate
'ActiveCell.Offset(1, 0).Select
Sheets("Database").Range(ActiveCell, ActiveCell.End(xlDown)).Copy
'Selection.Copy
Windows("dataoutput.xlsx").Activate
'Sheets("Sheet1").Range("I17").Select
'Range("I17").Select
Sheets("Sheet1").Range("I17").PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks _
:=False, Transpose:=False
Windows("fdatabase.xlsx").Activate
Sheets("Database").Range("A2").Select
'Cells.Find(What:="Address", After:=ActiveCell, LookIn:=xlFormulas, LookAt _
' :=xlPart, SearchOrder:=xlByRows, SearchDirection:=xlNext, MatchCase:= _
' False, SearchFormat:=False).Activate
'ActiveCell.Offset(1, 0).Select
'Range(Selection, Selection.End(xlDown)).Select
Sheets("Database").Range(ActiveCell, ActiveCell.End(xlDown)).Copy
'Selection.Copy
Windows("dataoutput.xlsx").Activate
'Sheets("Sheet1").Range("A17").Select
'Range("A17").Select
Sheets("Sheet1").Range("A17").PasteSpecial Paste:=xlPasteValues, Operation:=xlNone, SkipBlanks _
:=False, Transpose:=False
Application.ScreenUpdating = True
MsgBox "Done!"
End Sub
The code shows previous lines that were commented out to help you understand where the changes were made and hopefully to better follow the code logic.