SETFILTER blank for a field is not working in range Case

Hi ,
I have a text field “G/L Account Range” which has a values in range Ex. 7110…7193 , 6198|6150 . I have to filter this field to non blank values as there are some records with blank values. When I write a code:
CostType.SETFILTER(“G/L Account Range”,’<>%1’,’’);
I am getting following error:

The filter ‘<>’’’ on the G/L Account Range field in the Cost Type table must specify an interval. You can use two permitted formats for filters that specify an interval: * A Selects values equal to A. * A…Z Selects values between A and Z, inclusive.

Can someone suggest how can I specify a blank filter for this field?