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i do extractions on a day to day basis, when i extract i give groups of blocks a room number which is a tag in my attributes, due to the size of drawings and the amount of blocks i use i have to manually give the groups a room number by selecting them and inputing the room number. even when taking my time when looking at the excel i find that some blocks do not have a room number due to me missing them, i want to know is there any way for me to search my dwg to find out if the tag room number has not been filled in on the blocks in my drawing. as the extraction excercise is for a costing process. i use autocad 2011

please advise if you can?