need help with null values in datediff sql query

in sql query while doing datediff I want to take into consideration null values too

this is what i have

    SUM(CASE WHEN DATEDIFF(day, LoadDate, StartDate) BETWEEN 0 AND 2
        THEN 1 ELSE 0 END) AS 'Testfield'

In the above scenario start date can either be some date or null. If its null I want to make it today's date.  can we do that.
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slightwv (䄆 Netminder) Commented:
I'm thinking it should go like:
DATEDIFF(day, LoadDate, ISNULL(StartDate,GETDATE()))

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Query Syntax

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