Dynamic graph w/formulas in the cell range

Ok, I've got a graph using Dates as the X-axis. I've got formulas in the Date column (col A) that say if a cell in Col B has a value, add 1 to the Date from the cell above it. So, if A20 = 5/2/11 and B21 has a value, A21 will display 5/3/2011 and so on. I'm using the OFFSET function to make my graph's range dynamic, but it seems Excel is seeing my formulas in the "blank" date cells as "values" and it's picking up those cells (using the example above, A22 and beyond) in the dynamic range, so my graph of 2011, only up to May, is is showing condensed and roughly half-empty instead of dynamically only charting through the current date. Is there a way around this?