File Path - Concatenate

I am using the concatenate function to create a filepath,

using values in A1, A2 and A3 within the path to determine the location of the excel workbook i am referencing to.

this function gives me the correct file name as a string, how can i then use this to take data from a cell within this filepath, entering it into a cell?

=CONCATENATE("P:\",A1,"\",A2," - ",A3,"MRS.xls]Spine'!$B$8")
gives me the string for the filepath

Try =INDIRECT(CONCATENATE("'[P:\",A1,"\",A2," - ",A3,"MRS.xls]Spine'!$B$8"))

Yep have done, now working fine, some grammatical errors in relation to the filename and missing ' before the P:/,

thanks for the feedback