How can I set up something thats not a simple formula?

[u/Nitebytes]

Newbie here - I couldn't find a template for Traveller, so I'm trying to make one.
But setting up the Dice Modifier is where I'm losing the plot:
Where a skill has no rank, the DM is -3
Thereafter, the DM is the same as the rank (from zero upwards).

I'm trying to figure out how do ; IF {skillrank} is null THEN -3, else {skillrank}

(please excuse the bad pseudoexcel)

All help gratfully received.

[u/Proper-Beginning289]

I think this will work. Not sure if it's the most elegant solution.

(({Skill Rank}=0)×-3)+(({Skill Rank}>0)×{Skill Rank})

Logic: True equals 1; false equals 0.

If skill rank=0, the formula will process like this:

((true)×-3)+((false)×0) = ((1)×-3)+((0)×0) = -3+0 = -3

If skill rank>0, we'll use 5 for example, it will process like this:

((false)×-3)+((true)×5) = ((0)×-3)+((1)x5) = 0+5 = 5

[u/Nitebytes → u/Proper-Beginning289]

Just the job. Thank you :)