Cancel Command

I am trying to get my program to cancel a send e-mail command if certain things aren't filled out. Instead it is supposed to pop up with a message and then put the pointer in that field. The message box pops up, but the e-mail command is not cancelled. Can someone please tell me what I am doing wrong?

Private Sub SubmitAddCmd_Click()
On Error GoTo Err_SubmitAddCmd_Click

Dim stDocName As String
Dim strEmail As String
Dim strMailSubject As String
Dim strMsg As String
Dim strCopy As String
'Make sure MMS Job# is entered
If IsNull(MMSJob) Then
MsgBox "Please enter the MMS Job#"
[MMSJob].SetFocus
Cancel = True
'Make sure Client's name is entered
ElseIf IsNull(Client) Then
MsgBox "Please enter the Client's name"
[Client].SetFocus
Cancel = True
'Make sure job name is entered
ElseIf IsNull(Job) Then
MsgBox "Please enter the job name"
[Job].SetFocus
Cancel = True
'Make sure CSR name is entered for this job
ElseIf IsNull(CSR) Then
MsgBox "Please enter the name of the CSR for this job"
Cancel = True

'Make sure date job submitted button was clicked
ElseIf IsNull(Submitted) Then
MsgBox "Please click on the 'Date Job Submitted' button"
'[SubmittedCmd].SetFocus
Cancel = True
'Make sure mail date was entered
ElseIf IsNull(MailDate1) Then
MsgBox "Please enter a mail date for this job"
' [MailDate1].Value
Cancel = True
End If

'E-mail booking sheet to scheduling office in snapshot format
stDocName = "BookingRpt"
strEmail = "jhutton@merklenet.com;jsayers@merklenet.com"
strCopy = "rgarneriii@merklenet.com;"

strMailSubject = MMSJob & " " & Job

DoCmd.SendObject acSendReport, stDocName, acFormatSNP, strEmail, strCopy, , strMailSubject

Exit_SubmitAddCmd_Click:
Exit Sub

Err_SubmitAddCmd_Click:
MsgBox Err.Description
Resume Exit_SubmitAddCmd_Click

'Add new record
DoCmd.DoMenuItem acFormBar, acRecordsMenu, acSaveRecord, , acMenuVer70
DoCmd.GoToRecord , , acNewRec


End Sub

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