How to generate random numbers until sum of difference is 3000?

I need to generate random numbers until the condition(sum of the difference of each random number is 3000.) is satisfied.

and random numbers are already generated from the truncated normal distribution.

I already try to use while loop while(1) and if , but it didn't work properly.

How can I generate new random number sequence with the condition?

truncnorm_rn <- rtruncnorm(1000,0,30,0,1)

a <- 0
b <- 0
c <- 0 # sum of diffrences between truncnorm random number 
d <- NULL # New sequnce with condition

while(1){
         a <- truncnorm_rn[1]
         b <- truncnorm_rn[2]
         c <- sum(a - b)
         if(c > 3000) break
}