Error in set modifier ad hoc element list : ',' or ')' expected

[Fred12]

Hello, I try to do a sum with set analysis and variables.

Here my code : 

Sum({$<PERIODE={$(test1)}>}[VM])

+

Sum({$<PERIODE={$(test2)}>}[VM])

In test1, I have : 

=SubField(GetFieldSelections(PERIODE), ',' ,1)

in test2, I have :

=SubField(GetFieldSelections(PERIODE), ',' ,2)

If I do only  Sum({$<PERIODE={$(test1)}>}[VM])    then it works,  but if I add second sum, it put me error.

How can I solve it please.

Thanks in advance

[NadiaB]

@Fred12 

If the calculation works with the fist variable, probably the evaluation of the second one is returning something that is causing the problem, there is something that =SubField(GetFieldSelections(PERIODE), ',' ,2) is returning that is not working fine, if you using this in a text table, instead of using =SubField(GetFieldSelections(PERIODE), ',' ,2) as part of a calculation, just create another measure with that calculation (=SubField(GetFieldSelections(PERIODE), ',' ,2)) so you can see what is being returned and identify what is braking the calculation. 

Hope it helps. 

[vinieme12]

enclose in single quotes, also you must ensure there are always at least 2 selected values in PERIODE field

Sum({$<PERIODE={'$(=test1)'}>}[VM])

+

Sum({$<PERIODE={'$(=test2)'}>}[VM])