custom measure to start from period based on a property up to current perio

I want to define a custom measure which always takes the data from a fix period up to the period chosen.

This fixed period is defined by a property on the time period (TIME_IND = C). The C stands for current period.

Anybody a clue how to write this MDX statement ?

I don't know how to sum the data starting from TIME.TIME_IND=C up to the current member...

Thanks

Nico