Argument not Optional

Sub Button3_Click(Tsht As Worksheet)
Dim FlagR1 As Range
Dim FlagR2 As Range
Dim FlagR3 As Range
Dim FlagR4 As Range
Dim FlagR5 As Range
Dim FlagR6 As Range
Dim FlagR7 As Range
Dim FlagR8 As Range
Dim FlagR9 As Range
Dim FlagR10 As Range

Dim credit As Range
Dim debit As Range

Set Tsht = ThisWorkbook.Sheets("MASTER USD UPLOAD")
Set FlagR1 = Tsht.Cells.Range("B21:B40")
Set FlagR2 = Tsht.Cells.Range("B42:B48")
Set FlagR3 = Tsht.Cells.Range("B50:B54")
Set FlagR4 = Tsht.Cells.Range("B56:B96")
Set FlagR5 = Tsht.Cells.Range("B98:B112")
Set FlagR6 = Tsht.Cells.Range("B114:B123")
Set FlagR7 = Tsht.Cells.Range("B125:B130")
Set FlagR8 = Tsht.Cells.Range("B132:B144")
Set FlagR9 = Tsht.Cells.Range("B146:B147")
Set FlagR10 = Tsht.Cells.Range("B149:B166")

Set credit = Tsht.Cells.Range("J180")
Set debit = Tsht.Cells.Range("I180")

    For Each cell In FlagR1
    cell.value = "O"
    Next
    For Each cell In FlagR2
    cell.value = "O"
    Next
    For Each cell In FlagR3
    cell.value = "O"
    Next
    For Each cell In FlagR4
    cell.value = "O"
    Next
    For Each cell In FlagR5
    cell.value = "O"
    Next
    For Each cell In FlagR6
    cell.value = "O"
    Next
    For Each cell In FlagR7
    cell.value = "O"
    Next
    For Each cell In FlagR8
    cell.value = "O"
    Next
    For Each cell In FlagR9
    cell.value = "O"
    Next
    For Each cell In FlagR10
    cell.value = "O"

End Sub

Here is my code, for a simple button. I have been playing around with it for hours, so it may look odd.

I am trying to fill in cells, within certain ranges, when the button is clicked, however, I keep getting the "Argument not Optional" error, no matter what I change.