I pushed some Aconcagua extensions to
http://smalltalkhub.com/mc/SeanDeNigris/AconcaguaAddOns/main/The package relevant to Magritte specifically is . This gives you MAMeasureDescription, which represents an Aconcagua Measure. It mostly acts like a number field mapped to its amount. You just have to tell it which unit to use to convert the amount number into a Measure.
Example usage:
MAMeasureDescription new
accessor: #replacementPrice;
label: 'Replacement Price';
unit: AmDollar new;
yourself
Then, you can type 100 in a Magritte form and "100 dollars" will be saved to the model. Enjoy!
Cheers,
Sean