Generating random number promela spin

I'm newbie to Promela Spin and I would like some advices. In Promela Spin's documentation, says that there is no random function in order to generate random numbers from a specific range.

So right now I'm working on something which requires to choose each time a random row from an array, until all rows are finally chosen. I thought of generating each time a random number between the range of 0 - length_of_array and use it as an index for the array in order to get a random row. Unfortunately this way will not work because random number generation function does not exist here.

Can you suggest me an alternative solution guys ?

Thanks!