There are several reasons for GP Users to disable PO Number field in PO Entry, in order to not override the Next PO Number sequence in POP Setup.

And there are several methods and tools (Dex, VBA, etc) in accomplishing that. I have tried my bit in getting this functionality extended in PO Entry form.

Please find & download the chunk here: Disable PO Number in PO Entry

PRODUCT DETAILS:
1. Version: 10.4.4
2. Name: PO Number Disable
3. Product ID: 1983
3. Dictionary: POD.DIC
4. Forms Dictionary: F1983.DIC
5. Reports Dictionary: R1983.DIC

COMPATIBILITY:
1. Compatible GP Version: Dynamics GP 10.0 SP4

IMPORTANT:
1. This chunk is not a part of Microsoft Dynamics GP Products. This is a Custom Chunk developed by me.
2. I will be more than happy to improve this based on Users Feedback, but I cannot assure that all feedbacks would be met immediately or within a desired time.
3. This particular functionality works only in PO Entry Form.
4. Test this once in your Test Environment before using it on your Live Environment.
5. Please make sure that you have read the Limitations section in this post completely and you have understood that.

FUNCTIONALITY:
1. Once user selects a PO Type (Standard, Blanket, etc) and bring the focus to PO Number field, this chunk will allow GP to generate the Next PO Number from the POP Setup.
2. Then it immediately locks the PO Number field.
3. Then it takes the focus back to Buyer ID field.
4. Once you save the PO, it again releases the field.

LIMITATIONS:
1. Since the PO Number field had to be locked from user changing the PO Number value, users won’t be able to enter any PO Number directly on the PO Number field.
2. For instance, if a user wants to open an existing PO Number which he/she knows readily and does not require a Lookup, this functionality may prevent them from entering that PO Number.
3. In a nutshell, to edit an existing PO, user must use PO Number Lookup at all times.

I will update this post with an upgraded chunk as and when a feedback is addressed. I will also update the link above by adding a Readme File explaining the removal of this product from GP Folder and Dynamics.set.

VAIDY