Disable delete on subform

I have a Form "Invoice" that depending on its status, when loading I disable all fields so they are not editable.

The issue is that I have SubForms within that Form. I can disable the fields of the SubForm, however, the red "x" button still shows at the left of each line item allowing the user to delete the entire line item.

Is there a way to disable that delete line item button (red "x")?

Thanks,