You can - it isn't fully automatic, but neither is actually making the assembly on the shop floor.
What you need is to do is add two Component Parameters (not parameters in the part) to each component in the Assembly. One will be the Item Number and the other is the Assembly Step. I usually use the String type for parameters that don't have to be a number.
Then, for each sheet, set up a Repeat region** that filters out all except the matching step and use the asm.cparam.Item_Number instead of the default rpt.item (I think that's it) and set the Table Properties to use the asm.cparam.Item_Number as the balloon source. The rpt.qty should add up only the items that aren't excluded by the repeat region filter.
If you add the display of the Component parameters to the model tree view in the Assembly window, you can just click on any entry - if it doesn't have a value, Creo will prompt for the parameter type and the value; if it already has a value you can just type a new one. For entering the assembly step I'd create a mapkey that does it all (one key to edit the parameter, enter the type, and add the step string for each step); for the others a mapkey to set the parameter type.
**The can be more than one repeat region per sheet; this problem doesn't require that.