Like another sales order document, quotation document is also have rejection feature that applied in line items. Due to cancel the process of this quotation into sales order, the field reason rejection is able to be used to handle this requirement. By choosing one reason in this field, you might think that this item is no longer be able to be transferred into sales order. SAP provide standard routine to handle this.
In copy control Sales Order to Sales Order (VTAA), choose appropriate source document and target document. Then in item category you used, double click on that. In item details screen, use routine 301 to handle this.

The program of this routine can be found from t-code VOFM, from menu bar Copying requirements > Orders.
Display routine 301 by double click on it.
Here are the lines of the code you may read before you want to make changes or modification. By assistant from your ABAPER or you read it by yourself by helping from t-code SE16N then you will find the meaning of this code fragment, you can test this routine also by doing debugging on it.
VBAP~ABGRU : Reason rejection code
VBUP~RFSTA : Reference status
- ‘ ‘ : Not Relevant
- A : Not yet processed
- B : Partially processed
- C : Completely processed