Just combine the two blocks of code into one, so that the same code updates the two tables and subforms (the merged bit is shown in red):
Code:
Private Sub Form_AfterInsert()
Dim strSQL As String
' insert rows into Tbl_tblAuditMsg table
strSQL = "INSERT INTO tblAuditMsg(AuditID,MsgID) " & _
"SELECT " & Me.AuditID & ", MsgID " & _
"FROM tblMsg"
CurrentDb.Execute strSQL, dbFailOnError
' requery subform to show new rows
Me.subform1.Requery
' insert rows into Tbl_tblAuditFactor table
strSQL = "INSERT INTO tblAuditFactor(AuditID,FactorID) " & _
"SELECT " & Me.AuditID & ", FactorID " & _
"FROM tblAuditFactor"
CurrentDb.Execute strSQL, dbFailOnError
' requery subform to show new rows
Me.subform2.Requery
End Sub