A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
If you are using the userform to insert the value into the worksheet that creates the value in column C then use the command button that inserts the value to update the textbox.
e.g.
Private Sub CommandButton1_Click()
Dim xlSheet As Worksheet
Set xlSheet = ActiveWorkbook.Sheets(1)
'Do stuff
Me.TextBox1.Value = xlSheet.Range("C" & xlSheet.Range("C" & xlSheet.Rows.Count).End(-4162).Row)
End Sub