Diagnosis
You are attempting to make a mass selection of more than 1000materials. This would cause you problems with system performance. Thereis currently no option available for branching to a more detailedmaterial selection screen here, prior to passing your selection on tomodule functions.
The maximum number of 1000 for this function has been defined as theSAP standard value on the basis of experience.
You can only increase this number by means of a modification (ABAPinclude MWWCONST - counter MAX_Z_AV_...). If you take this route,however, SAP can no longer guarantee a high level of systemperformance.

Procedure
Use different selection criteria or enter the individual materialnumbers manually in the module items.