I have an equation in A1:

=if(H1<45,"",H1)

This is fine, if H1 is less than 45, then A1 stays blank. I don't want
it to have a zero, because that would show up in a plot, it should be
blank. But, in cell B1, I want the equation:

=10+A1

This works fine if A1 has a value (<45), but it won't work if A1 has
"" in it. I want:

10 + "" = 10

not:
10 + "" = #VALUE!

Any suggestions without making "" be a zero?

Chris