Need assitance in writing script

Hi Guys,

I need assitnace in writing new script whcih need to look for stage number and start executing from that stage. 

I Understand run key location would be right place for script path. Please correct me if i am wrong. 

Expected script 

define global variables(envirnoment varibles)

StageCheckFunction()

Stage 1:

Restart function(After restart it need to start from stage 2) 

Stage 2:

Stage 3:

End of script

Can anyone please help me with script. 

Thanks in advance

Thanks,

Vamsi