Check For Duplicates Using VBA

I have created a userform that inputs employees names in to a sheet called employee list. It works well, now I want to take it a stage further and check to see if the employee being entered is already in the list and if so let the end user decide whether enter the new data or save the data already in the list.

Private Sub cmdOK_Click()
ActiveWorkbook.Sheets("Employee List").Activate
Range("A1").Select
Do
If IsEmpty(ActiveCell) = False Then
ActiveCell.Offset(1, 0).Select
End If
Loop Until IsEmpty(ActiveCell) = True
ActiveCell.Value = txtName.Value
ActiveCell.Offset(0, 1) = txtLast.Value
ActiveCell.Offset(0, 2) = TxtNum.Value
ActiveCell.Offset(0, 3) = cboCourse.Value
If optIntroduction = True Then
ActiveCell.Offset(0, 4).Value = "Operative"
ElseIf optIntermediate = True Then
ActiveCell.Offset(0, 4).Value = "Team Leader"
Else
ActiveCell.Offset(0, 4).Value = "Manager"
End If

Range("A1").Select
End Sub