Hi Brian - your request seems far too vague to enable anyone to answer it precisely, but in principle an HLOOKUP might look like this . . .
Where . . .
A1 is the lookup value, could be a date
B1:C2 contains the lookup table, in this example on a separate tab called SUMMARY.
In this example the range B1:C1 would contain the reference list (of dates ?) to be compared against the single lookup value in A1.
2 defines how many rows to go down in the lookup table, in this case 2, so that the value from row 2 is returned
FALSE defines an exact match for the lookup test.
Excel formula help is reasonably good in explaining this.