A 3-GeV light source named Taiwan Photon Source (TPS) at National Synchrotron Radiation Research Center (NSRRC) is under construction, and is scheduled for commissioning in 2013/2014. An SRF module of KEKB type has been selected for the TPS as the accelerating cavity of its storage ring. The SRF valve boxes, as part of the cryogenic transfer system, stabilize the cryogenic operational conditions required for various needs of SRF operation. The SRF operation requires a large dynamic variation in the cryogenic loading that challenges appropriate sizing of the cryogenic regulation valves to minimize the pressure drop and concurrently to maintain a fine regulation of pressure. Here, we report our design considerations for an SRF valve box with emphasis on highly stabilizing the helium pressure for SRF operation with a dual-return valve scheme. The estimated fluctuations of pressure due to finite accuracy of the valve opening decrease to a tenth of what is obtained from the conventional single return-valve scheme.