how to put condition in rdlc ?

Question

i have a rdlc in which first column is number and second column is date

 

in database there are two types of date 

1) start date eg 4/419

2) end date  eg 20/9/20

 

number	date	xyz	abc	pqr
p456365646	startdate
r4546465646	enddate

 

i have to put expression in date column in such a way that  

if the number starts from p it should take start date

if the number starts from r it should take end date