First of all - thanks a lot for all thee replies and answers - I am always a bit amazed of the kindness and efforts of people in this forum ..
Zizi64 wrote:Are you using Apache OpenOffice or LibreOffice?
I am using both. LibreOffice 5.1.3.2 on Win7 and AOO 4.1.x ( not sure ) on UBUNTU.
At my work, all the computers are with AOO, and all my private machines have both AOO and LibreOffice as portables.
Zizi64 wrote:The Libreoffice can hadle more than 3 conditions for a cell or a cellrange.
I know that more than 3 conditions can be used - But somehow there are not operators (AND,OR .. ) between them . That makes it more difficult .
See my original file for example.
But regarding this - how exactly does conditions being handled ? Does calc goes over all of them, or if the first condition is satisfied - it skip the next ?
lack of operators really makes it a bit hard to understand .
Zizi64 wrote: See the created cell styles on the SideBar, and the six conditions in the CF window.
Your solution indeed works , just like I wrote in the original question ( 6 separated styles ) .
I also wrote that this is what I want to avoid , having 7 or more currencies can be a bit challanging .
Villeroy wrote:First condition formula: STYLE(INDEX($F$1:$F$3;$D$2;1))
Yes ! - Thanks , this seems to be a great way to reduce the 3 primitive functions I have made into 1 - and if fact , When I first applied it - it worked wonderfully .
Well - actually a bit strange But on the right track :
But - when I started to try and apply more conditions - weird display problems started to occur .
I saw flickering of cells and some other problems ( not seeing selections range ).
So I looked up the STYLE() function, which I did not knew before , and saw that it is actually time-dependent , and constantly updating ( and calculating );
Then I tried to remove the time parameter : STYLE(INDEX($F$1:$F$3;$D$2;)) - But same problem .
The second thing I tried , was to apply this formula with a much simpler condition :
Let's take simple two color scale , with formula
ISODD(ROW()) and
ISEVEN(ROW()) - and voila -
But alas - seems like this condition is not working at all for me ( a hidden bug ?? ) - even when applied ALONE .
( Can see attached file for both bugs - display errors, and not working conditions )
Now, allow me to rant a bit

( And by all means - this is not about the work that people do - which is wonderful. it is more about overall strategy )
The main problem , in a broader view of how OOO handles this issue , as I see it is this :
Styling and Formatting ( Numbers in particular ) are NOT interchangeable terms.
A number FORMAT is the like TYPE of data whereas STYLE is more connected to how to DISPLAY this data .
Thinking in terms of ( simple ) programming , a Number type can be INT, STRING , FLOAT etc . It should not influence the way that number is DISPLAYED .
Continuing in terms of simplified example - that most people can understand , lets take a simple web-app with PHP/HTML/CSS.
In PHP I would cast the TYPE of the number ( not a must , but let's assume I do ) , but the DISPLAY of that number will be handled by HTML / CSS.
In CALC, the "FORMATTING" function is totally wrong in concept .
I assume that this is inherited from the need to "copycat" excel , which in turn inherited this behavior from it's long ( and OLD ) legacy.
( This is another rant I have : the seemingly need / want of OOO/Libre to "Follow" or " Copy" excel - which is already bad in terms of UX/UI - instead of being a leader in design and function - but that is not for this thread

)
The right way to handle that issue would be to separate STYLING and FORMATTING . Especially when Numbers are discussed . In fact - the "numbers" tab has no business of being in the "styles" dialog .
The number " FORMAT " or "TYPE" should be a property of the cell, not related to the display style .
If that was really the case , many problems related to Formatting, could have been resolved .
For example , there is no reason why one should use a complicated mechanism of " conditional formatting " to achieve simple alternating background .
Wouldn't it be much more simple to put that is the "background " menu like an option ?
Anyhow, enough with the rants , I am still looking for a solution - so any test / try is very welcomed .