It's kind of like, if your avg initial bet actually is $30, and, say, you are playing with an overall EV of 1%, and you play 100 hands per hour, then in 5 hours your EV would only be $150 anyway kind of thing.
So maybe knowing what to expect over how long, along with knowing a likely high range (1 or 2 stand dev say) is where it all begins and then decide just what amounts might arouse suspicion.
Is there any specific reason (like game, spread, etc) that leads you to believe your avg bet actually will be around $30?
How much did you think you might win anyway that would raise eyebrows in 4-5 hours, say maybe $500 or $1000, and how likely would that result be anyway? Good chance, as rukus suggested, you might not really have to worry about it anyway.
Begin at the beginning.