Run commands in parallel

Hi,

I have a script that runs an application "CALCAPP.exe" using values from passing parameters:

\\PRCServer09\APPS$\CalcApp.exe -f \\PRCServer09\Data$\dlymkt.xml -r \\PRCServer09\Rules$\mktRules.xml -d CALCDATA

It's processing a large amount of data taking around 3 hours. Problem is the app calcapp.exe is unable to handle large file, however able to process multiple smaller data-file at the same time. So, I split the source data-file into 4 pieces and want to kick-off 4 parallel process at the same time. After split the files are: dlymkt_1.xml, dlymkt_2.xml, dlymkt_3.xml, dlymkt_4.xml that will be processed by CalcApp.exe.

Commands:
\\PRCServer09\APPS$\CalcApp.exe -f \\PRCServer09\Data$\dlymkt_1.xml -r \\PRCServer09\Rules$\mktRules.xml -d CALCDATA
\\PRCServer09\APPS$\CalcApp.exe -f \\PRCServer09\Data$\dlymkt_2.xml -r \\PRCServer09\Rules$\mktRules.xml -d CALCDATA
\\PRCServer09\APPS$\CalcApp.exe -f \\PRCServer09\Data$\dlymkt_3.xml -r \\PRCServer09\Rules$\mktRules.xml -d CALCDATA
\\PRCServer09\APPS$\CalcApp.exe -f \\PRCServer09\Data$\dlymkt_4.xml -r \\PRCServer09\Rules$\mktRules.xml -d CALCDATA

With current setup powershell will execute these 4 statements sequentially that I don't want. I want to kick-off all 4 statements at the same time, which means all runs parallel. Any ideas please?