sorry for late response,i already know this solution and implemented.
one more thing i have to mention here.whenever i change any selection from the combox at that time query is also refreshing for the below heat map,so once combobox place blank cell to destination cell stiil that query refreshing,once refresh completed the selected value placed into the destination Cell(nothing replacing blank with selected value after refresh complete).
to avoid this i put dynamic visibility for that combobx,like this should enable once query refresh completed but no use
Thanks,
Prasad