Use 'unless'
If he isn't ill, he'll come to see us at the weekend.
He will come to see us at the weekend unless he is ill.
If they ___________ (come), I ____ (be) really surprised.
If they come, I will be really surprised.
When you _________ (arrive) , we _________ (go) to the cinema together.
When you arrive , we will go to the cinema together.
Please, call me __________ you are back.
Please, call me when you are back.
you /get back late/ I / be / angry
If you get back late, I will be angry.
She won't go to the university if she doesn't study more.
She won't go to the university unless she studies more.
If it ________(rain), we ________________ (not/go) to the beach.
If it rains, we won't go to the beach.
She _________ (not help) until we ________ (ask) her to do it.
She won't help) until we ask her to do it.
There could be a letter from Bill today. ___________ there is, please tell me.
There could be a letter from Bill today. If there is, please tell me.
Susan / eat / too many sweets / she / get / fat
If Susan eats too many sweets, she will get fat.
If we don't hurry, we won't get there on time.
We won't get there on time unless we hurry.
You ___________ (regret) it if you ______(eat) all that cake.
You will regret it if you eat all that cake.
I _________ (go) for a walk as soon as it _______ (get) warmer.
I will go for a walk as soon as it gets warmer.
I'm going to town tomorrow. ____________ you need anything, phone me.
I'm going to town tomorrow. If you need anything, phone me.
The weather / be / as sunny tomorrow as it was today / we /go / surfing
If the weather is as sunny tomorrow as it was today, we will go surfing.
if you don't stop playing computer games, you won't meet anyone.
You won't meet anyone unless you stop playing computer games.
I think he ___________ (come) if you ___________ (invite) him.
I think he will come if you invite him.
Before you______ (buy) this shirt , you _______ (have to) try it on.
Before you buy this shirt , you will have to try it on.
I'm thirsty. __________ I come home, I'll have a cup of tea.
I'm thirsty. When I come home, I'll have a cup of tea.
I /feel / good / the next day / I / go / to bed early
I feel good the next day if I go to bed early.
If you come back late, we won't wait for you.
We won't wait for you unless you don't come back late.
He ___________ (find) the answers if he ___________ (look) at the back of the book.
He will find the answers if he looks at the back of the book.
You _______ (can ) take photos inside the museum as long as you ______(not use) a flash.
You can take photos inside the museum as long as you don't use a flash.
I'm going to spend my holidays in England. ______ I am there, I'll buy two pullovers.
I'm going to spend my holidays in England. When I am there, I'll buy two pullovers.
My sister won't go to Spain if she doesn't lose weight.