How change Under-relaxation factors during iteration
 

Hi everybody
I want to create a BATCH file that let me to change the under-relaxation factors during my simulation in order to make it faster: something like this

rcd folder/file.cas
it 300
momentum=0.3
it 400
momentum=0.6
.....

can anyone tell me if it's possible and the commands of the file?

Thanks in advance! :)