Tonumber on 4-digits number gives #ERROR (BO 4.1 SP03)

Question

Hi Guys,
I have a strange problem.
While using some Input Controls and formulas, I had to return a value from variable created as a number.
I have 3 variables, 1 for Month, 1 for Quarter, 1 for Year.
I return the month\qt\year in the following structure:
"ToNumber([Month])" (Same for QT and Year).
This works well on month and qt, but somewhy Year is giving #Error.
So I tried some things, and got to the conclusion that 4-digits number doesn't work well with "ToNumber".
my problem is I can't do "Formatnumber" inside the "tonumber" because my variable is sometimes Text and it doesn't work.
Any suggestions for by-passing the issue when trying to make "tonumber" on 4-digits?
(I tried creating blank cell with the value "=Tonumber(1000" - Got error as well)
Thank you very much,
Or

Answer 1

Ok I'll try to simplify it.
The report is a comparison report between two periods.
That means the user can select year-qt-month, but twice.
6 input control in total, 3 for each period.
eventually i'm presenting a table with 2 "restricted key figure" (the measure with a "where" term) according to the user's filter.
Now, when the user choose "all values" option, the report returns #ERROR because I'm comparing the variable inside my calculated measure formula.
I need to check for each period if the user chose a value or he didn't, and if he did - then that selected period should be inside the "Where" condition - if he selected "All values" than the "where" should be without any mentioning of that period inside.
that said, the last variable is a 6-combination formula that, according to selected values, activates different calls to the measure, with the difference of the "Where" condition inside.
And to do that, I have to make a check for isnumber\something like that so I'll know that the user didn't select a specific period.
I know that the explanation is detached and long, sorry. That was the reason I chose to ask my question in general.
Thank you all in advance,
Or