Increment data in Avalon Microsequencer

Hi,

this post is not about NIOS problem, but program avalon microsequencer. I can some time critical operation move from Nios to avalon microsequencer. And I have basic problem - I can't increment data in on-chip memory. How can I do it? The INC(data) only increment immediate data loaded to CNT_REG, not data from memory or DATA_REG.