I have standing orders that come in at different time intervals. I don't want to create 52 unique purchase orders so I created one, used memorized transactions/automatically enter. However, I do not want the purchase order number to change but every time it automatically enters the next one, it changes the purchase order in sequence. So, I tried to create the purchase order and leave the purchase order number blank hoping that when it auto enters it will remain blank, it stills automatically enters the next number is sequence. 

By keeping the purchase order number the same, when I receive the standing order it is easy to find in the open po list and receive against the purchase order. But, because it keeps changing the number each time it automatically enters to a next sequenced number, I can't find it AND it may use a purchase order number that I haven't entered yet. 

I have tried leaving the purchase order number blank. I have also tried to find a preference to turn it off. The only preference I can find is to stop auto numbering journal entries, not other forms. 

What is the solution?