Mobile BI for IPAD - Key date BEx variable

Hi expert,

i need to create a WEBI mobile report on Ipad based on BEx query with customer exit variable key date.

I would that if the user , on Ipad device, doesn't insert a date for the key date variable, these variable is enhanced by the customer exit in background.

Are there some limitations to implement this WEBI mobile report on SAP BI mobile ?

Thanks.

Andrea