Comparing one date to another

I swear this worked when I tried it a couple of days ago... now suddenly it doesn't

It's not doing the bit in bold, checking the date entered is greater than the date in txtDateReg.

Dim FindPatients As Range

Set FindPatients = myPatients.Find(what:=cboPatients, lookat:=xlWhole)
txtDateReg.Value = FindPatients.Offset(0, 3)
txtDateReg.Enabled = True

myDate = InputBox("Enter the Patient Admitted Date", "Date Entry", Date)

If myDate <> "" Then
    Do Until IsDate(myDate)
    If IsDate(myDate) = False Then
        MsgBox "Date is not entered"
        myDate = InputBox("Enter the Patient Admitted Date", "Date Entry", Date)
            If myDate < txtDateReg.Value Then
                Do Until myDate > txtDateReg.Value
                MsgBox "Registered Date is after admitted date!"
                myDate = InputBox("Enter the Patient Admitted Date", "Date Entry", Date)
                Loop
            End If
    End If
    Loop
End If