A form cannot be opened in Design View in an ACCDE file. Is there a reason why you need to open the form in Design View?

To change its record source because a table is created by code and now, the user must fill this table with this template form so each time the user open the form, its a different table as record source depending on the user choice

You don't need to switch to Design View to set the Record Source.

Me.RecordSource = "TableName"

Me.RecordSource = "QueryName"

Me.RecordSource = "SQL Statement"

Ill try it again but it doesn't seem to work when Im in the Accde file. My code is in a click button event to open this template form. Does it matter if the form is open or close to execute this code(me.recordsource)

I you're opening the Form with a button on a different Form you have to specify the name of the form you want to set the Record Source for.

Example:
DoCmd.OpenForm "TemplateF"
Forms!TemplateF.RecordSource = "CustomerT"

Value From a Form

I tried the code you provided and it doesn't work, even in the regular accdb file. You can see my original code preceded by '. This code with design view is working perfectly in the accdb file but not in accde, Im confused! (the name of the table is in a hidden field (NomTabOp)in the form containing the button for this code)
    DoCmd.OpenForm ("Entrees_F")
    'DoCmd.RunCommand acCmdDesignView
     Forms!Entrees_F.RecordSource = Me.NomTabOp
    'DoCmd.Save
    'DoCmd.RunCommand acCmdFormView

Hi Simon, what exactly doesn't work?  Changing the recordsource in design view is the only way to save the recordsource into the form permanently, while changing the RecordSource property with VBA as Kevin suggested does not save it into the form -- when you reopen the form, the old recordsource remains.  Is that what you mean by doesn't work?

Thank you all for your help. I was expecting the same behaviour as my original code so it would change the recordsource in the form property sheet. I was working with blank tables as recordsource so I wasn't seeing that it was working because each time I looked in the property sheet, it was the original record source, so problem solved. Thanks!