Passing data from an subform to an form

[ToreSweden]

When i make an textbox in an form with this : =[Invoice Detail Table Underform].[Form]![Totalprice]

I got:  #Name?

Where to search for this issue?

I checked spellings and that the format is the same.

Best regards

Tore

[#2]

The correct grammar for this event is [forms]![form name]![subform name]![control name]
I guess You just missed “ [forms]![form name]!”
Hope it works~

[#3]

@SeanZhang 

Well, tried Your grammar with the same results.

The thing is that I have watched a couple of youtube clip showing My grammar as the correct one.

Example: https://www.youtube.com/watch?v=BhLFYE0RNJA

And the expression builder giving the same results.

Something else must be the issue here.      Can You suggest something?

Best regards

Tore