lookup_ext how to

Hi,

Can anyone tell me if this is possible through lookup_ext function?

My requirement is this:  ltrim_blank (look_up_column)= Input_table_column

so I decided to use the SQL Custom function:

However I keep getting this error:

Found erroneous expression <__AL_LOOKUPEX_TRAN lookup_ext ([DS_ELECTION_STG.TEISAPPL.SCHOOL_TYPE_L, 'PRE_LOAD_CACHE', 'MAX'],

[SCHOOL_TYPE_ID], [NULL], [SCHOOL_TYPE_CODE, '=', Municipal_Line_Check_default.NAME_SCHOOL_SUPPORT], [], [], ['SELECT TRIM(' '

SCHOOL_TYPE_CODE) FROM SCHOOL_TYPE_L']) SET ("run_as_separate_process"='no', "output_cols_info"='<?xml version="1.0" SCHOOL_TYPE_ID  encoding="UTF-8"?><output_cols_info><col index="1" expression="no"/>

</output_cols_info>' )>. Check its syntax and fix this expression.

has anyone done this before?

TIA