SAP Message 26090 - Enter AScEx when entering screen number

Diagnosis
You have entered a screen which is to replace the standard Basicdata screen 0101 in program SAPLCV00 for the document type.

System Response
The system requires an entry for the program in which the PBO and PIAform routines for the alternative screen are processed.

Procedure
In field AScEx, enter the name of the program which processesthe alternative screen.