how to bind an InputField to a DDIC structure

I need to link an InputField view element to a search help (H_T158B). The search help requires two input parameters of the following types: BWART and TCODE.

One parameter (type BWART) needs to be linked to the InputField, the other one will be hardcoded to a specific value.

SAP told me I need to create a DDIC structure with two fields (BWART and TCODE) and bind the DDIC structure to the InputField.

as per the link below

http://help.sap.com/saphelp_nw04s/helpdata/en/de/408e41392fb85fe10000000a1550b0/frameset.htm

there should be a button "DDIC binding to" but I do not see this button in my context binding screen.

how can I map my InputField to a DDIC structure?