My thanks to you Greg, this is now working brilliantly!

Private Sub cbThreat_Change()

    If cbThreat.ListIndex <> -1 Then cbThreat.BackColor = RGB(255, 255, 255)
lbl_Exit:
    Exit Sub
End Sub

Private Sub txtThreat_Change()

    If Len(txtThreat.Text) > 0 Then txtThreat.BackColor = RGB(255, 255, 255)
lbl_Exit:
    Exit Sub
End Sub

Private Sub cbHarm_Change()

    If cbHarm.ListIndex <> -1 Then cbHarm.BackColor = RGB(255, 255, 255)
lbl_Exit:
    Exit Sub
End Sub

Private Sub txtHarm_Change()

    If Len(txtHarm.Text) > 0 Then txtHarm.BackColor = RGB(255, 255, 255)
lbl_Exit:
    Exit Sub
End Sub

Private Sub cbOpportunity_Change()

    If cbOpportunity.ListIndex <> -1 Then cbOpportunity.BackColor = RGB(255, 255, 255)
lbl_Exit:
    Exit Sub
End Sub

Private Sub txtOpportunity_Change()

    If Len(txtOpportunity.Text) > 0 Then txtOpportunity.BackColor = RGB(255, 255, 255)
lbl_Exit:
    Exit Sub
End Sub

Private Sub cbRisk_Change()

    If cbRisk.ListIndex <> -1 Then cbRisk.BackColor = RGB(255, 255, 255)
lbl_Exit:
    Exit Sub
End Sub

Private Sub txtRisk_Change()

    If Len(txtRisk.Text) > 0 Then txtRisk.BackColor = RGB(255, 255, 255)
lbl_Exit:
    Exit Sub
End Sub

Private Sub txtRationale_Change()

    If Len(txtRationale.Text) > 0 Then txtRationale.BackColor = RGB(255, 255, 255)
lbl_Exit:
    Exit Sub
End Sub

Private Sub EnterBut_Click()

    If cbThreat.ListIndex < 1 Then
        cbThreat.BackColor = RGB(102, 255, 255)
        cbThreat.SetFocus
        MsgBox "Select threat level!", vbExclamation + vbOKOnly, "Triage Hub"
        Exit Sub
    End If
    
    If Len(txtThreat.Text) = 0 Then
        txtThreat.BackColor = RGB(255, 255, 204)
        txtThreat.SetFocus
        MsgBox "Enter threat text!", vbExclamation + vbOKOnly, "Triage Hub"
        Exit Sub
    End If
    
    If cbHarm.ListIndex < 1 Then
        cbHarm.BackColor = RGB(102, 255, 255)
        cbHarm.SetFocus
        MsgBox "Select harm level!", vbExclamation + vbOKOnly, "Triage Hub"
        Exit Sub
    End If
    
    If Len(txtHarm.Text) = 0 Then
        txtHarm.BackColor = RGB(255, 255, 204)
        txtHarm.SetFocus
        MsgBox "Enter harm text!", vbExclamation + vbOKOnly, "Triage Hub"
        Exit Sub
    End If
    
    If cbOpportunity.ListIndex < 1 Then
        cbOpportunity.BackColor = RGB(102, 255, 255)
        cbOpportunity.SetFocus
        MsgBox "Select opportunity level!", vbExclamation + vbOKOnly, "Triage Hub"
        Exit Sub
    End If
    
    If Len(txtOpportunity.Text) = 0 Then
        txtOpportunity.BackColor = RGB(255, 255, 204)
        txtOpportunity.SetFocus
        MsgBox "Enter opportunity text!", vbExclamation + vbOKOnly, "Triage Hub"
        Exit Sub
    End If
    
    If cbRisk.ListIndex < 1 Then
        cbRisk.BackColor = RGB(102, 255, 255)
        cbRisk.SetFocus
        MsgBox "Select risk level!", vbExclamation + vbOKOnly, "Triage Hub"
        Exit Sub
    End If
    
    If Len(txtRisk.Text) = 0 Then
        txtRisk.BackColor = RGB(255, 255, 204)
        txtRisk.SetFocus
        MsgBox "Enter risk text!", vbExclamation + vbOKOnly, "Triage Hub"
        Exit Sub
    End If
    
    If Len(txtRationale.Text) = 0 Then
        txtRationale.BackColor = RGB(255, 255, 204)
        txtRationale.SetFocus
        MsgBox "Enter rationale!", vbExclamation + vbOKOnly, "Triage Hub"
        Exit Sub
    End If
    
    Tag = 1
    Hide
lbl_Exit:
    Exit Sub
End Sub