What is MST?

MST is short for "Monetary Standard".

Or also:
MST = Master = Currency of the Company
Cur = Currency (needs also a transdate or exchangeratefield)

AmountMST refers to the base currency you keep your records of the system in, i.e. "Company currency".
So for example when recording an invoice you keep the amounts both in your company currency, i.e. MST (for example DKK), and the invoice currency, for example EUR.

source: http://blogs.msdn.com/b/palle_agermark/archive/2007/04/24/what-is-mst.aspx

Inventory Transaction modifications

STOCK

When stock physically enters or leaves AX, it passes through class InventUpd_Physical.
Methods:

• UpdatePhysicalReceipt (stock entering)
• UpdatePhysicalIssue (stock leaving)

Both at line “updPhysical+= inventTrans.Qty”

You can use the movement variable to ask whatever you need to enter into / modify the inventTrans record.

FINANCIAL

Financial values for these transactions are handled the same way, through class InventUpd_Financial.
methods:

• UpdateFinancialReceipt
• UpdateFinancialIssue