Add a dynamic variable value for a attribute in fetchxml

Hi Guys,

Everytime and everywhere i see in fetchxml people use only harcoded values i got a scenerio were i need to pass a  dynamically  a string variable please suggest note this c# code

string dynamic ="xyz";

string fetch3 = @"<fetch version='1.0' output-format='xml-platform' mapping='logical' distinct='false'>
<entity name='hd_cuscatmust'>
<attribute name='hd_cuscatmustid' />
<attribute name='hd_cusseqnum' />
<attribute name='createdon' />
<order attribute='hd_cusseqnum' descending='false' />
<filter type='and'>
<condition attribute='hd_cusmercod' operator='not-null' />
<condition attribute='hd_cuscatcod' operator='not-null' />
<condition attribute='hd_cusmercod' operator='eq' value=""+dynamic+@"">
</filter>
</entity>
</fetch>";