MarketPress: Unique SKU, Transaction, and User Numbers

Hi,

I want to be able to set unique SKU, transaction and user ID numbers.

I found this forum post that suggested creating a template function to display the SKU (and noting that the SKU is stored in the "mp_sku" post meta value as a serialized array): https://premium.wpmudev.org/forums/topic/display-item-number-on-product#post-100579.

I assume i would have to do the same for the transaction and user ID numbers. Questions:

1. What fields do I use to modify:
a. the transaction number
b. the user ID number

2. How would you write formulas to:
a. set the length of the number
b. set the starting number
c. show a random output number (not sequential)
d. show a number that auto increments per a pre-defined formula

Many thanks!