You can use the left function to determine if the first letter is a 'P'. You can check this in the validate ot lost focu event.
if left(text1,1)="P" then...
Add the UCase function if it is not case sensitive.
if Ucase(left(text1,1))="P" then...
Another method would be to seed the text box with a "P" before the user eneters anything. Or use the keypress event to only allow the first letter to be a "P".
if len(text1)=0 then
if not keyascii=<value> then keyascii=0
end if
Where <value> is the ascii value for the letteer 'P'. You will need to look that up in the ascii character set.
Thanks and Good Luck!
zemp