would you be happy if the chart  showed data  until the last entry, but
the line  went right across the chart, so that the right edge was the
last entry? I'm thinking a dynamic range.

Two solutions to this maybe:
1. The uglier solution, but quicker: where you've got
=IF(OR(A2=0,B2=0),"",D2*1.5)
change it to
=IF(OR(A2=0,B2=0),NA(),D2*1.5)
The chart  won't plot  the #N/A cells  but will draw a line  directly from
one valid point to the next, ie. no gaps. The ugly side of this is the
presence of a lot of cells displaying  #N/A in the worksheet.

2. Leave your formula  as it was, but create a named range with a
formula: Go into Insert|Name|Define... and enter  say 'graph' (without
the single quote marks) in the 'Names in workbook' field. Then in the
'Refers to:' field paste something similar to the following:
=(IF(Sheet1!$E$2:$E$31<>"",Sheet1!$E$2:$E$31,NA()))
Then click the 'Add' button and close the dialogue box.
This will create a series  of values  like the cells in solution (1)
above, in the defined name 'graph' , and this is what we'll plot. Go
back to the chart and click on one of the points of your series so
that the whole series is selected. Look in the formula bar and you'll
see the likes of:
=SERIES(,,Sheet1!$E$2:$E$31,1)
It's the
'Sheet1!$E$2:$E$31'
that needs changing to
'Sheet1!graph,1)'
(without quote marks) and press Enter. (It may change to
=SERIES(,,Yourfilename!graph,1)
that's fine.)
Now you should see the same chart as in (1) above  but without all the
#N/As in the worksheet.

A third solution is to create a dynamic named range instead of the
static one above when a chart as proposed in my previous answer would
be produced.

This is very strange. I KNOW I have done plots  that simply omit non exsistent
data, but
couldn't figure out how i Used to do it [brain tells me there 'was' a
"Plot-Zero-Values"
option, but brain has been wrong B4].

I tried an X-Y plot  - nope.

This may get you closer to a solution...
Here's what is the strangest.
I found that If I Paste Values (from the formula  cells), the chart  STILL
plots "empty" cells
as zero.
HOWEVER, if I Clear Contents in that cell, then the point and connecting
lines are
omitted!

So...
A "" is interpreted as a zero.
A Pasted Value of "" is interpreted as a zero.
a Cleared cell  is undefined / unplottable.


So, do a TypeName on the three types of "blank" cells( "" in formula, a Pasted
"" from a
formula and a fully Cleared cell) to see what they are.

This may mean you'll need a macro  to Clear a copy of the Zero valued cells.

Wa-Da-Ya-Think?

I suspect you'll find  that the times you did that were on column  charts,
rather than line  charts. It's relatively unusual to want to omit items in
line charts.

My recollection is clearly that it was on line  charts. I rarely do
column charts. However, it is entirely possible that I may have
simply Cleared the values  of the zero/blank cells. I also rarely do
plots of more than a few dozen values, so manual intervention for the
desired effect  is always a possiblity.

I am, however, still curious what the types of those cells  are...

So I checked. A Cleared cell  is Type "Empty".
A cell containing "" is an [obviously null] "String"...which, of
course, "makes sense"...

SO, perhaps a macro  to clear those pesky null cells (a copied
version) is in order.