It seems so simple...

[salgud]

I've done a number of posts here and tried a dozen different ways, but I
can't get the following code to trap a user input error (no input) and
leave the userform open so they can enter the data, then just continue the
program.

The userform code for if they click "Enter":

Private Sub cbEnter_Click()
sTribeNameUI = frmTribeNameSMCY.cbTribeName.Text
sCYUI = frmTribeNameSMCY.cbCY
sServMonthUI = frmTribeNameSMCY.cbServMonth


If sTribeNameUI = "" Or sCYUI = "" Or sServMonthUI = "" Then
MsgBox "Please select a Tribe Name, a Service Month and" & Chr(10) & _
" a Calendar Year!", vbOKOnly
With Me.cbTribeName
.SelStart = 0
.SelLength = Len(.Text)
.SetFocus
End With
End If

End Sub

The main routine:
Public Sub CreateTribalSheet()

Set wbTribal = ThisWorkbook
Set wsSource = wbTribal.Sheets("Source")
The following is a subprocedure to enter some data from a userform.

Public Sub TribeNameServDate()
Application.ScreenUpdating = True
frmFacil.Hide
frmTribeNameSMCY.Show
Application.ScreenUpdating = False

Unload frmTribeNameSMCY

ws.Range("A1").Value = sTribeNameUI & " Turnaround Report"

ws.Range("D3").Value = sServMonthUI

iServMonth = Month(DateValue(ws.Range("d3") & " 1,2009"))

iPayrollMonth = iServMonth + 1

If iPayrollMonth > 12 Then
iPayrollMonth = iPayrollMonth - 12
End If

sPayrollMonth = Format(28 * iPayrollMonth, "MMM") 'converts integer month
to text month
ws.Range("C3").Value = sPayrollMonth

If iPayrollMonth < 6 Then
sSFY = Right(sCYUI, 2)
Else
sSFY = Right(sCYUI + 1, 2)
End If

ws.Range("J3:K3").Select
Selection.NumberFormat = "@"
ws.Range("J3") = Right(sCYUI, 2)
ws.Range("K3") = sSFY
ws.Range("A1").Select

End Sub

The userform has 3 comboboxes (so user's entries are consistent to make it
easier to work with the dates) and the code for the Enter button is:

Private Sub cbEnter_Click()
sTribeNameUI = frmTribeNameSMCY.cbTribeName.Text
sCYUI = frmTribeNameSMCY.cbCY
sServMonthUI = frmTribeNameSMCY.cbServMonth


If sTribeNameUI = "" Or sCYUI = "" Or sServMonthUI = "" _
Or sCYUI = 0 Then
MsgBox "Please select a Tribe Name, a Service Month and" & Chr(10) & _
" a Calendar Year!", vbOKOnly
With Me.cbTribeName
.SelStart = 0
.SelLength = Len(.Text)
.SetFocus
End With
End If

End Sub

What I want to happen is that if any of the 3 data entries are blank, the
userform reappears and gives the user another chance to enter the data, and
the progam continues as before. How do I do this?
Thanks!