Need a Urgent help for one expression based on below scenario

I have two files called
HSMMECO_GHS_SKV_RIP_20121030.txt
HSMMECO_GHS_SKVRAP_RIP_20121030.txt .I need to loop these files and load in to table using foreach loop .I am trying to get a expression in a Filespec property,which will turn these files to a common format as shown below .

HSMMECO_GHS_SKV*.txt

Please help me to get that expression.Thanks in advance!