1) In the blank cell enter =NA() which shows as #N/A and is ignored by the
chart engine. Or if using formula use something like =IF(A10, B1/A1, NA())

2) Click chart; use Tools | Options; open Chart tab and specify how missing
data is to be treated.

best wishes
--
Bernard V Liengme
Microsoft Excel MVP
www.stfx.ca/people/bliengme
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