Not clear why you need two tables (MyForms and tblMyTable) or since you have two tables you are concerned about deleting the existing forms in tblMytable when you are adding new forms to MyForms but based on the info provided in post #1 perhaps
Code:
INSERT INTO MyForms ( frmName )
SELECT frms.Name
FROM (SELECT Name
FROM msysobjects
WHERE Type=-32768) AS frms LEFT JOIN tblMytable ON frms.Name = tblMytable.formName
WHERE tblMytable.formName Is Null
You can easily convert the sql to be executed in vba