Help/Support How to generate a random number in limit space

[paintokill 0 Huawei Mate8 7.0]

Hello there, i need some help about arm modding, first here is the code region look like:

 

At now I cam use 'NOP' to remove the

CMP RO, #1
BNE loc_A5664C

to run the MOV R1, #4, I also can set #4 to #3 set it value to 3.

But my question is how can i generate a random number to set R1 other values like betweent 2 and 4,  3 and 4? i tried use BL to other function but program itself will stuck nothing will be execute, any help?

 

P.S: here's my random number generate code already get, but i dont know where should i put it

MOV	R1, #0
MOV	R2, #0x64
BL	#0x11A982C
CMP	R0, #0x55
BHI	#0x1C
MOV	R1, #4
B	#0x20
MOV	R1, #3