Create wildcards for the items that are not filled out by the user.

>Hi all
>
>I would like to know how to filter a grid on a form which contains a view for a table. The user will be allowed 4 comboboxes to input the filter condition. These 4 cbo are not always necessarily filled and as and when any or all of them are filled the records are to be filtered progressively, so I doubt I will be able to use ?vp_para1... as not all of them will be filled.
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>Please advise.