replacing #N/A values with zero values

I have a cell that is looking up values in another sheet using HLOOKUP....
when it doesn't find a value it returns a #N/A value....
I have tried using an IF statement with an imbedded ISNA or ISERROR or
ERROR.TYPE function to have it return a zero in the event of #N/A and the
actual value if it is able to find what it is looking up....
I need to convert the #N/As to zeros so I can use the sum function by merely
highlighting a range with my mouse...

Thanks.