Forward and Backward Pass Activity on Node Diagrams in MS Project 2010

I want to make Forward and Backward Slack Activity on Node Diagrams in MS Project 2010.

I display the Network Diagram view and choose Format > Box Styles. I Click the More
Templates button and in the Data Templates, dialog, select an
existing template and copy it. I Give the new template a name in
the Data Definition dialog window. Towards the bottom of the
Data Definition dialog window in the "Choose Cells" section I
can specify which fields to place in which area.

I want to define four custom number fields ES, LS,
EF, and LF.

ES = ProjectDateDiff([ProjectStart],[EarlyStart])/[MinutesPerDay]

EF = ProjectDateDiff([ProjectStart],[EarlyFinish])/[MinutesPerDay]

LS = ProjectDateDiff([LateStart],[ProjectFinish])/[MinutesPerDay]

LF = ProjectDateDiff([LateFinish],[ProjectFinish])/[MinutesPerDay]

but it seems MS Project doesn’t allow formulas or custom fields.

How can I do a formula in a box field or formula ? Is it possible ?