variable assignment

I need to pass a global variable to the child grid. The screen structure is pretty complex, however the idea should be simple.
After I click on the record in Grid1 (the top one), I want the child grid filtered based on common field (Dis_ID)

Created OnClick Ajax Event with the code like this:

[var_glo_disease_id]=({Dis_ID});

where: Dis_ID is a unique record ID

I filter child grid in SQL section

SELECT


WHERE
DiseaseId=[var_glo_disease_id]

everything works fine, but I do not have an ADD (new rocord button on the child grid). Any ideas ?

Arthur