If
Value = (Date())
Then
IF INLIST(ALLTRIM(STR(day(txtstart.value))),"01","1")
Should work also
IF day(txtstart.value)= 1
Should work
Otherwise you can use
IF INLIST(TRANSFORM(DAY(CTOD(TRANSFORM(txtstart.value)))),"01","1")
OR
IF DAY(CTOD(TRANSFORM(txtstart.value)))=1

AT