need help with level editor drag and drop object

so, need help with one trick with level editor element "writing value to drag and drop array" if mouse mouse button released and if object state isn't drag and drop. My main problem is if dragging object 1st time it will create object in right positions, but if i load array 2st time it will create 2nd object in 2nd positition. I dunno how clear current position with value 0 and write 1.
Sorry for my english. So here is my small example. You'll see what i mean.

1. Create object
2. Drag and Drop to wherever you whant.
3. If object isn't in drag and drop condition - write 1 to xmouse/16, ymouse/16
4. Clear cell where we write 1 value if object in drag and drop condition (0 value to xmouse/16, ymouse/16)

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