[Xymon] show RRD Graph based on daily values

I want to display a graph with values that change only once a day. The check is a clientside script in which te sslstatus of a website is calculated I translate the values (T, U, F, E, D, C, B, A-, A and A+) into a percentage default=0, E=25, D=50, C=75, B=80 and A-=90 A=95 and A+=100 when I run the testsscript every 5 minutes the graph will appear nice.

but when I run the script once or twice a day nothing wil appear. Is it possible to get a graph without writing a script that checks every 5 minutes?