How to select multiple variable values via URL parameter?

I'm trying to create a URL that will select multiple variable values and run an existing bookmark via parameters. The URL below works fine with a single value but I can't get it to work for more than one value:

http://bwserver/irj/servlet/prt/portal/prtroot/pcd!3aportal_content!2fcom.sap.pct!2fplatform_add_ons!2fcom.sap.ip.bi!2fiViews!2fcom.sap.ip.bi.bex?BOOKMARK=<bookmarkID>&CMD=LDOC&BI_COMMAND_1-BI_COMMAND_TYPE=SET_VARIABLES_STATE&BI_COMMAND_1-VARIABLE_VALUES-VARIABLE_VALUE_1-VARIABLE_TYPE=VARIABLE_INPUT_STRING&BI_COMMAND_1-VARIABLE_VALUES-VARIABLE_VALUE_1-VARIABLE=<varname>&VARIABLE_SCREEN=&BI_COMMAND_1-VARIABLE_VALUES-VARIABLE_VALUE_1-VARIABLE_TYPE-VARIABLE_INPUT_STRING=<varvalue>

This is in BW 7.3

Thanks,

Jason