Extract number between a position and the first comma after it

Hello, I need some help coming up with this formula.

text string:
R1:50,R2:71,R3:18,R4:50,R5:128,R6:27,R7:113,R8:50,R9:10,R10:80,R11:67,R12:123,R13:80,R14:28

the first part R followed by a number can be any integer from R1 to R10000
the number after ":" can be any integer from 1 to 50000

I need a formula given the position of the R portion extract the number.

say for R14, I need to extract 28
for R12, I need to extract 123
etc etc

thanks so much in advance