It’s grammatical to use “should” like “if”:
- Should you need me, call.
- I’ll be available should she ask for me.
- Should my mother call, let her know I’ll be back shortly.
It’s also grammatical to use “should” for “would”:
- If you call me, I should hope that I answer.
- When I ask you a question, I should expect that you not lie to me.
- Were you not to seize this opportunity, I should think you mad.
HOWEVER, is it grammatical to use both of these grammatical conventions at the same time? In a conditional sentence, can “should” be used in both the protasis and the apodosis?
Should you desire to go, I should hope you do. (If you desire to go, I would hope you do.)
Should he come, I should like to meet him. (If he comes, I’d like to meet him.)
- We should expect a call from you should there be any problem. (We would expect a call from you if there’s any problem.)
It’s perfectly possible to use two shoulds in the same conditional:
Should anyone phone asking when the drilling’s going to stop, I should imagine we’ll all be finished by 2 o’clock.
Of course, it’s not strictly accurate to think that the first should here is replacing if. Here’s the same sentence with if reinserted:
If anyone should phone asking when the drilling’s going to stop, I should imagine we’ll all be finished by 2 o’clock.
Here we can see both if and should together in the same protasis. The first sentence uses subject-auxiliary inversion to mark the conditional protasis. The if has been dropped and the Subject, anyone and the auxiliary verb should have changed places.