Can any body help in IDoc field handling

Hi every body,

i am working Idoc( INVOIC01) to File scenario, which is related to Invoice processing. i got one problem as below,

there is one segment E1EDP01 under that i am having several E1EDP02. Each E1EDP02 may have different QUALF(qualifier). now i should check weather qualifier equals to 002 or not, if Qualifier is 002, then i will map the field(ZEILE) under qualifier 002 to target element. the problem here is some times though qualifier is 002 the source element ( ZEILE ) will not populate in the IDoc.