In B4
=VLOOKUP($E$1,INDIRECT($A4&"!$A$1:$T$104"),16)
In C4
=VLOOKUP($E$1,INDIRECT($A4&"!$A$1:$T$104"),18)
In D4
=VLOOKUP($E$1,INDIRECT($A4&"!$A$1:$T$104"),20)

Copy down the summary sheet

But you may run into problems if you start adding data to the empoloyees sheets beyond row 104

You could always use a cell to check the last filled in row and concatenate that with the INDIRECT function