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AlremeithiMohamed 

This version will create a text file; it will prompt you for the folder and filename.

It'll be slow, though.

Sub GenerateSheets()
    Dim NumLetters As Long
    Dim NumSheets As Long
    Dim NumRows As Long
    Dim Wbk As Workbook
    Dim Wsh As Worksheet
    Dim i As Long
    Dim Filename As Variant
    Dim f As Integer
    Dim r As Long
    NumLetters = Application.InputBox(Prompt:="How many letters do you want to use (max 26)?", Type:=1)
    If NumLetters < 1 Or NumLetters > 26 Then
        Beep
        Exit Sub
    End If
    NumSheets = Application.InputBox(Prompt:="How many sheets do you want to create?", Type:=1)
    If NumSheets < 1 Then
        Beep
        Exit Sub
    End If
    If NumSheets > 4000 Then
        If MsgBox(Prompt:="Warning! This could take a long time! Do you want to continue?", _
                Buttons:=vbYesNo + vbQuestion) = vbNo Then
            Exit Sub
        End If
    End If
    NumRows = Application.InputBox(Prompt:="How many rows per sheet do you want to fill?", Type:=1)
    If NumRows < 1 Or NumRows > 1048576 Then
        Beep
        Exit Sub
    End If
    Application.ScreenUpdating = False
    Set Wbk = Workbooks.Add(Template:=xlWBATWorksheet)
    For i = 1 To NumSheets
        Set Wsh = Wbk.Worksheets.Add(After:=Wbk.Worksheets(Wbk.Worksheets.Count))
        Wsh.Range("A1").Resize(NumRows).Value = "This"
        Wsh.Range("B1").Resize(NumRows).Value = "That"
        Wsh.Range("C1").Resize(NumRows).Formula = "=BASE(ROW()-1+" & (i - 1) * NumRows & "," & 10 + NumLetters & ", 6)"
        Wsh.Range("D1").Resize(NumRows).Value = "Other"
        Wsh.Range("E1").Resize(NumRows).Value = "Something"
        DoEvents
    Next i
    Application.DisplayAlerts = False
    Wbk.Worksheets(1).Delete
    Application.DisplayAlerts = True
    Application.ScreenUpdating = True
    Filename = Application.GetSaveAsFilename(FileFilter:="Text File (*.txt),*.txt", Title:="Save to Text File")
    If Filename = False Then
        Exit Sub
    End If
    f = FreeFile
    Open Filename For Output As #f
    For i = 1 To NumSheets
        For r = 1 To NumRows
            Print #f, Worksheets(i).Range("C" & r).Text
        Next r
    Next i
    Close #f
End Sub