Hi IB12013,
Try this, note that this will give 00.04.30 not 4.30 although those would be easy changes but this should give you a start:
numberVar TotalMinutes := 270; //I'm using your example of 270 minutes here
numberVar vhr := int(TotalMinutes/3600);
numberVar vrem := remainder(TotalMinutes,3600);
numberVar vmin := int(vrem/60);
vrem := remainder(vrem,60);
numberVar vsec := int(vrem);
stringVar dot := ".";
stringVar vshr := IIF(vhr<10,"0"+ToText(vhr,0),ToText(vhr,0));
stringVar vsmin := IIF(vmin<10,"0"+ToText(vmin,0),ToText(vmin,0));
stringVar vssec := IIF(vsec<10,"0"+ToText(vsec,0),ToText(vsec,0));
stringVar timestring := vshr+dot+vsmin+dot+vssec;