Fixed trials within randomized (BGR) blocks?

[maya]

I was thinking maybe someone will be able to help me with my problems here : I'm trying to run an ER task that design like that:
We have 12 blocks of slides, 5 slides in each block. While the same 5 slides that make up each block need to be the same across participants, the block order needs to be randomized.
We also need a sound label to be presented before slides. For example, "1A, 1B, 1C, 1D, 1E" need to be presented before each of the slides in the first block, and "2A, 2B, 2C, 2D, 2E" need to be presented before each of the slides in the second block. Although we're randomizing the blocks, we are NOT randomizing the sound labels. In other words, "1A, 1B, 1C, 1D, 1E" need to precede the 5 slides in the first block for each participant, the actual block of slides will be different for each participant due to randomization.
i don't know how to solve this problem so if someone has a solution pls let me know
thanks
maya