TextBox to act as Standard NAV date Filter

Here how is my tip and trick works for this.

1. Declare a record variable that has a field datatype Date in it. Lets say we use the Date record as variable recDate.
2. Declare a text variable for your TextBox to act as Standard NAV date Filter. Lets use myTextDate.
3. Put myTextDate on the SourceExpr property of your textbox.
4. On the validate trigger of your textbox. Put the code like this.

recDate.SETFILTER("Period Start", myTextDate);
myTextDate := recDate.GETFILTER("Period Start");

5. Done.

Note : If you input the character listed below in the textbox:

M = Will return the date of Monday in the current week.
T = Will return the date of Tuesday in the current week.
W = Will return the date of Wednesday in the current week.
TH = Will return the date of Tuesday in the current week.
F = Will return the date of Friday in the current week.
S = Will return the date of Saturday in the current week.
SU = Will return the date of Sunday in the current week.

If you want to capture the character 'T' as today or 'W' as workdate then you must have a LONG code like this.

myTextDate := UPPERCASE(myTextDate);

//---- Make TU as Tuesday
IF STRPOS(myTextDate, 'TU') > 0 THEN BEGIN
  recDate.SETFILTER("Period Start", 'T');
  IF STRLEN(myTextDate) <> 2 THEN BEGIN
    WHILE STRPOS(myTextDate, 'TU') <> 0 DO BEGIN
      myTextDate := COPYSTR(myTextDate, 1, STRPOS(myTextDate, 'TU') - 1) +
         recDate.GETFILTER("Period Start") +
         COPYSTR(myTextDate, STRPOS(myTextDate, 'TU') + 2, STRLEN(myTextDate));
    END;
  END ELSE
    myTextDate := recDate.GETFILTER("Period Start");
END;

//---- Make WE as Wednesday
IF STRPOS(myTextDate, 'WE') > 0 THEN BEGIN
  recDate.SETFILTER("Period Start", 'W');
  IF STRLEN(myTextDate) <> 2 THEN BEGIN
    WHILE STRPOS(myTextDate, 'WE') <> 0 DO BEGIN
      myTextDate := COPYSTR(myTextDate, 1, STRPOS(myTextDate, 'WE') - 1) +
         recDate.GETFILTER("Period Start") +
         COPYSTR(myTextDate, STRPOS(myTextDate, 'WE') + 2, STRLEN(myTextDate));
    END;
  END ELSE
    myTextDate := recDate.GETFILTER("Period Start");
END;


//---- for the character T as TODAY
IF STRPOS(myTextDate, 'T') > 0 THEN BEGIN
  IF STRLEN(myTextDate) <> 1 THEN BEGIN
    WHILE STRPOS(myTextDate, 'T') <> 0 DO BEGIN
      myTextDate := COPYSTR(myTextDate, 1, STRPOS(myTextDate, 'T') - 1) +
         FORMAT(TODAY) +
         COPYSTR(myTextDate, STRPOS(myTextDate, 'T') + 1, STRLEN(myTextDate));
    END;
  END ELSE
     myTextDate := FORMAT(TODAY);
END;

//---- for the character W as WORKDATE
IF STRPOS(myTextDate, 'W') > 0 THEN BEGIN
  IF STRLEN(myTextDate) <> 1 THEN BEGIN
    WHILE STRPOS(myTextDate, 'W') <> 0 DO BEGIN
      myTextDate := COPYSTR(myTextDate, 1, STRPOS(myTextDate, 'W') - 1) +
         FORMAT(WORKDATE) +
         COPYSTR(myTextDate, STRPOS(myTextDate, 'W') + 1, STRLEN(myTextDate));
    END;
  END ELSE
     myTextDate := FORMAT(WORKDATE);
END;

recDate.SETFILTER("Period Start", myTextDate);
myTextDate := recDate.GETFILTER("Period Start");

Hope this works for you too