Extracting base currency in Sales and Purchase data.

Hi all,

I am not an AX developer, but have been working on producing data from dynamics ax into Qlikview. Please excuse my ignorance.

I am extracting from Purchase or Sales Table/Line. Values stored here are all in the currency chosen when creating record, not base currency.
I have come to realise that many other Tables have a field called amountMST, this of course is in base currency. (How useful.)
We may have many Sales in various currencies, we may also have different currencies in Misc Charges (MarkupTrans). If I wish to develop further in Qlikview I need to stick with one currency, as trying to convert is extremely difficult.
I believe Dynamics AX handles this automatically using amountMST method? Of course I am Selecting straight from the Database so I cannot use this.
Can you see the problem I have? what would you suggest or am I completely barking up the wrong tree?